Mass Transfer

Question 1

Mass transfer rate between two fluid phases does not necessarily depend on the __________ of the two phases.

• chemical properties
• physical properties
• degree of turbulence
• interfacial area

Answer 1

chemical properties

Question 2

In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is

• 0.50
• 0.60
• 2
• 1

Answer 2

0.50

Question 3

Fenske equation determines the

• maximum number of ideal plates.
• height of the distillation column.
• minimum number of theoretical plates.
• optimum reflux ratio.

Answer 3

minimum number of theoretical plates.

Question 4

The term “cooling range” in a cooling tower refers to the difference in the temperature of

• cold water leaving the tower and the wet bulb temperature of the surrounding air.
• hot water entering the tower and the wet bulb temperature of the surrounding air.
• hot water entering the tower and the cooled water leaving the tower.
• none of these

Answer 4

hot water entering the tower and the cooled water leaving the tower.

Question 5

Which of the following is the most suitable for extraction in a system having very low density difference ?

• Mixer-settler extractor
• Centrifugal extractor
• Pulsed extractor
• Packed extraction tower

Answer 5

Centrifugal extractor

Question 6

Total reflux in a distillation operation requires minimum

• reboiler load
• number of plates
• condenser load
• all (a), (b) and (c)

Answer 6

number of plates

Question 7

The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is

• +ve
• -ve
• zero
• none of these

Answer 7

+ve

Question 8

Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the

• relative volatility is reasonably constant.
• mixture (to be separated) shows negative deviation from ideality.
• mixture (to be separated) shows positive deviation from ideality.
• multicomponent distillation is involved.

Answer 8

relative volatility is reasonably constant.

Question 9

When the temperature and humidity of air is low, we usually use __________ draft cooling tower.

• natural
• forced
• induced
• none of these

Answer 9

natural

Question 10

Pick out the correct statement.

• In case of liquid-liquid extraction, no separation is possible, if the selectivity of the solvent used is unity.
• With increase in temperature, the selectivity of the solvent used in solvent extraction decreases.
• The selectivity of solvent used in solvent extraction is unity at the plait point.
• all (a), (b) and (c).

Answer 10

all (a), (b) and (c).

Question 11

__________ columns are used for liquid dispersion in a continuous gas phase.

• Packed
• Pulse
• Bubble cap
• Sieve plate

Answer 11

Packed

Question 12

Overall efficiency of the distillation column is

• the ratio of number of ideal plates to actual plates.
• the ratio of number of actual plates to ideal plates.
• same as the Murphree efficiency.
• always more than the point efficiency.

Answer 12

the ratio of number of ideal plates to actual plates.

Question 13

Which is the controlling factor for a drum drier?

• Diffusion
• Heat transfer
• Both (a) and (b)
• Neither (a) nor (b)

Answer 13

Heat transfer

Question 14

Drying operation under vacuum is carried out to

• dry those materials which have very high unbound mositure content.
• reduce drying temperature.
• increase drying temperature.
• dry materials having high bound moisture content.

Answer 14

reduce drying temperature.

Question 15

Air initially at 101. 3 kPa and 40°C and with a relative humidity of 50%, is cooled at constant pressure to 30°C. The cooled air has a

• higher dew point.
• higher absolute (specific) humidity.
• higher relative humidity
• higher wet bulb temperature.

Answer 15

higher relative humidity

Question 16

Separation of two or more components of a liquid solution can not be achieved by

• fractional crystallisation
• liquid extraction
• absorption
• evaporation

Answer 16

absorption

Question 17

At minimum reflux ratio for a given separation

• number of plates is zero.
• number of plates is infinity.
• minimum number of the theoretical plates is required.
• separation is most efficient.

Answer 17

number of plates is infinity.

Question 18

Relative humidity is the ratio of the

• partial pressure of the vapour to the vapour pressure of the liquid at room temperature.
• partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
• actual humidity to saturation humidity.
• none of these

Answer 18

partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.

Question 19

In batch distillation with constant reflux, overhead product composition __________ with time.

• increases
• decreases
• does not vary
• may increase on decrease, depends on the system.

Answer 19

decreases

Question 20

Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the __________ of a fibre.

• electrical resistance
• thermal conductivity
• strength
• none of these.

Answer 20

electrical resistance

Question 21

Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the

• latent heat
• humid heat
• specific heat
• sensible heat

Answer 21

specific heat

Question 22

To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)

• increase both ‘G’ and ‘S’.
• decrease both ‘G’ and ‘S’.
• increase ‘S’ and decrease ‘G’.
• increase ‘G’ and decrease ‘S’

Answer 22

increase ‘S’ and decrease ‘G’.

Question 23

The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________

• 1
• 0.5
• 10
• 0

Answer 23

1

Question 24

Dew point of a gas-vapour mixture

• increases with temperature rise.
• decreases with temperature rise.
• decreases with decrease in pressure.
• increases with increase in pressure.

Answer 24

decreases with decrease in pressure.

Question 25

Which of the following plays an important role in problems of simultaneous heat and mass transfer ? * Lewis number * Schmidt number * Prandtl number * Sherwood number

Answer 25

Lewis number

Question 26

In case of an absorber, the operating * line always lies above the equilibrium curve. * line always lies below the equilibrium curve. * line can be either above or below the equilibrium curve. * velocity is more than the loading velocity.

Answer 26

line always lies above the equilibrium curve.

Question 27

As the reflux ratio in a distillation coloumn is increased from the minimum, the * slope of the operating line in stripping section decreases. * number of plates decreases very slowly first and then more and more rapidly. * total cost first decreases and then increases. * liquid flow increases while the vapor flow decreases for a system.

Answer 27

total cost first decreases and then increases.

Question 28

Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve) * S2/S1 * S1/S2 * S1 - S2 * S1 x S2

Answer 28

S1/S2

Question 29

A plait point is the point on the solubility curve, where the tie line reduces to a point. What is the number of plait point for a ternery system containing two pairs of partially miscible liquids ? * 0 * 1 * 2 * 3

Answer 29

0

Question 30

Make up water is required in a cooling tower to replace the water lost by * evaporation * drift * blowdown and leakage * all (a), (b) and (c)

Answer 30

all (a), (b) and (c)

Question 31

Which of the following quantities need not be fixed before starting the design of a co-current absorber ? * Heat gain or loss * Flow rate of entering liquid * Flow rate of gas * None of these

Answer 31

Flow rate of entering liquid

Question 32

Mass transfer co-efficient of liquid is * affected more by temperature than that for gases. * affected much less by temperature than that for gases. * not affected by the temperature. * none of these.

Answer 32

affected more by temperature than that for gases.

Question 33

Absorption accompanied with chemical reaction is exemplified by the absorption of - ammonia in water. - benzol present in coke oven gas by wash oil. - SO2 in alkaline solution. - all (a), (b) and (c).

Answer 33

SO2 in alkaline solution.

Question 34

Which of the following unit operations makes use of Thiele-Geddes equation ? * Liquid-liquid extraction * Solid-liquid extraction * Multicomponent absorption with chemical reaction * Multicomponent distillation.

Answer 34

Multicomponent distillation.

Question 35

Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty ? * Sieve plate column * Bubble cap column * Randomly packed column * Wetted wall column

Answer 35

Wetted wall column

Question 36

The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is * natural draft cooling tower * induced draft cooling tower * spray chamber * none of these

Answer 36

spray chamber

Question 37

Chemisorption (chemical adsorption) is * same as "Van der Waals" adsorption. * characterised by adsorption of heat. * an irreversible phenomenon. * a reversible phenomenon.

Answer 37

an irreversible phenomenon.

Question 38

The rate of solid-liquid extraction is limited by the * phase change of the solute as it dissolves in the solvent. * diffusion of the solute through the solvent in the pores to the outside of the particle. * diffusion of the solute from the solution in contact with the particle to the main bulk of the solution. * all 'a', 'b' & 'c'.

Answer 38

all 'a', 'b' & 'c'.

Question 39

Raoult's law applies to the * all liquid solutions * non-ideal solution only. * non-volatile solute. * solvents.

Answer 39

solvents.

Question 40

In distillation columns, the number of bubble caps per tray primarily depends upon the * allowable liquid velocity. * allowable gas velocity. * allowable gas and liquid velocities. * feed composition.

Answer 40

allowable gas and liquid velocities.

Question 41

In distillation, overhead product contains * only one component * two components * any number of components * only saturated liquid

Answer 41

any number of components

Question 42

With increase in pressure, the relative volatility for a binary system * increases. * decreases. * remains same. * either (a) or (b), depends on the system.

Answer 42

decreases.

Question 43

Low viscosity absorbent is preferred for reasons of * rapid absorption rates and good heat transfer characteristics. * improved flooding characteristics. * low pressure drop on pumping. * all (a), (b) and (c).

Answer 43

all (a), (b) and (c).

Question 44

Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as * K ∝ D * K ∝ √D * K ∝ D^1.5 * K ∝ D^2

Answer 44

K ∝ D

Question 45

The McCabe Δ L law states that the * molar heats of vaporisation of components are nearly equal. * linear crystal growth rate depends on the degree of supersaturation. * linear crystal growth rate does not depend on the crystal size. * linear crystal growth rate depends on the crystal size.

Answer 45

linear crystal growth rate does not depend on the crystal size.

Question 46

Bollman extractor * is a static bed leaching equipment. * is used for extraction of oil from oilseed. * is a centrifugal extractor. * employs only counter-current extraction.

Answer 46

is used for extraction of oil from oilseed.

Question 47

The relation, Sc = Pr = 1, is valid, when the mechanism of __________ transfer is same. * heat and mass * mass and momentum * heat and momentum * heat, momentum and mass

Answer 47

heat and mass

Question 48

A coalescer in a mixer-settler liquid-liquid extraction coloumn * comprises of thin bed of substances of extended surface having high porosity. * helps in increasing the bubble size entering the settler. * helps in increasing the settling rate of the bubbles. * all 'a', 'b', & 'c'.

Answer 48

all 'a', 'b', & 'c'.

Question 49

For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will * increase * decrease * remain same * data insufficient, can't be predicted

Answer 49

increase

Question 50

Pick out the correct statement. * Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation. * A sharp decrease in pressure drop is an indication of flooding in a distillation coloumn. * Solvent used in extractive distillation should be of high volatility. * Flash distillation is suitable for separating components which have very close boiling temperature.

Answer 50

Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation.

Question 51

When the liquid phase and vapour phase of a binary system obeys Raoult's and Dalton's law respectively, the relative volatility is the ratio of * vapour pressure of component A to that of component B. * vapour pressure of component A to the total pressure. * vapour pressure of component A to the partial pressure of A. * partial pressure of component A to the total pressure.

Answer 51

vapour pressure of component A to that of component B.

Question 52

The operation involved when the soluble material is largely on the surface of an insoluble solid and is merely washed off by the solvent is called * decoction * percolation * elutriation or elution * none of these

Answer 52

none of these

Question 53

In the constant rate period of the rate of drying curve for batch drying, * cracks develop on the surface of the solid. * rate of drying decreases abruptly. * surface evaporation of unbound moisture occurs. * none of these.

Answer 53

surface evaporation of unbound moisture occurs.

Question 54

It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%). * 15 min * 51 min * 71 min * 94 min

Answer 54

71 min

Question 55

Agitator is provided in a crystalliser for * avoiding deposition on cooler surfaces. * formation of nuclei. * crystal growth. * all (a), (b) and (c).

Answer 55

all (a), (b) and (c).

Question 56

__________ diffusion is used for separating the isotopes of methane. * Thermal * Pressure * Concentration * Force

Answer 56

Thermal

Question 57

Ordinary diffusion process is also called __________ diffusion. * pressure * thermal * concentration * forced.

Answer 57

concentration

Question 58

Pick out the wrong statement. * Different solids have different equilibrium moisture curves. * Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column. * Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column. * Even a forced draft cooling tower can not cool water below the wet bulb temperature.

Answer 58

Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.

Question 59

Pick out the wrong statement pertaining to the rotary dryer. * Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12% of the inside diameter of shell. * Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.05 to 0.15. * Rotary dryer is suitable for drying sticky material. * Recommended peripherial speed of a rotary drier is in the range of 10 to 30 metres/minute.

Answer 59

Rotary dryer is suitable for drying sticky material.

Question 60

The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives * low pressure drop and high hold up. * high pressure drop and low hold up. * low pressure drop and low hold up. * high pressure drop and high hold up.

Answer 60

low pressure drop and low hold up.

Question 61

If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent. * 100 * > 100 * < 100 * none of these

Answer 61

> 100

Question 62

Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2. hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is * 25% * 50% * 70% * 90%

Answer 62

50%

Question 63

Raoult's law is applicable to the * ideal solutions * real solutions * mixture of water and alcohol * non-ideal gases

Answer 63

ideal solutions

Question 64

Weeping in a distillation column * increases tray efficiency. * provides large interfacial surface for mass transfer. * results due to very high gas velocity. * results due to very low gas velocity.

Answer 64

results due to very low gas velocity.

Question 65

In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of * area between operating line and 45° diagonal x-y diagram. * condenser and reboiler surfaces. * tower cross-section. * none of these.

Answer 65

area between operating line and 45° diagonal x-y diagram.

Question 66

Wetted wall tower experiment determines the * molal diffusivity. * volumetric co-efficient. * mass transfer co-efficient. * none of these.

Answer 66

mass transfer co-efficient.

Question 67

In McCabe-Thiele method, at infinite reflux ratio * the overhead product is minimum. * both the operating lines coincide with diagonal. * both (a) and (b). * neither (a) nor (b).

Answer 67

the overhead product is minimum.

Question 68

With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency * increases * decreases * remains same * may increase or decrease ; depends on individual design

Answer 68

increases

Question 69

Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the * packing may be crushed due to thermal expansion/contraction of the components of the equipments. * pressure drop in the equipment will be very high. * viscosity variation of the fluids may cause channeling/flooding. * none of these.

Answer 69

packing may be crushed due to thermal expansion/contraction of the components of the equipments.

Question 70

The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is * more * less * same * either more or less; depends on the system

Answer 70

same

Question 71

Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower. * wetted wall * bubble cap * perforated tray * packed

Answer 71

wetted wall

Question 72

Pick out the system with minimum boiling azeotrope at 1 atm. * benzene-toluene * ethyl alcohol-water * hydrochloric acid-water * all (a), (b) and (c)

Answer 72

ethyl alcohol-water

Question 73

Free flowing granular materials can be best dried in a __________ drier. * rotary * cylinder * drum * freeze

Answer 73

rotary

Question 74

In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction, * inversely * linearly * exponentially * none of these

Answer 74

linearly

Question 75

Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number. * Sherwood * Schmidt * Peclet * Stanton

Answer 75

Sherwood

Question 76

If the specific heats of a gas and a vapor are 0.2KJ/Kg.°K and 1.5 KJ/Kg.°K respectively, and the humidity is 0.01; the humid heat in KJ/°Kg. is * 0.31 * 0.107 * 0.017 * 0.215

Answer 76

0.215

Question 77

Liquid diffusivity is of the order of __________ cm^2 /second. * 0.01 * 0.1 * 10^-5 to 10^-6 * > 1

Answer 77

10^-5 to 10^-6

Question 78

The solvent used in liquid extraction should not have high latent heat of vaporisation, because - the pressure drop and hence the pumping cost will be very high. - it cannot be recovered by distillation. - its recovery cost by distillation may be prohibitatively high. - it will decompose while recovering by distillation.

Answer 78

its recovery cost by distillation may be prohibitatively high.

Question 79

At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid __________ that in dry packed tower. * is greater than * is lower than * is same as * cannot be predicted as data are insufficient

Answer 79

is greater than

Question 80

Molarity is defined as the number of gm moles of solute per __________ of solvent. * litre * kg * gm * c.c

Answer 80

litre

Question 81

The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around * 1 * 0.24 * 3.97 * 600

Answer 81

1

Question 82

Which of the following T-H diagram is valid for dehumidification operation ?

Answer 82

Question 83

An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii) * less number of trays are required. * composition of the residue remains unchanged. * more number of trays are required but the residue composition remains unchanged. * more number of trays are required and the residue composition is more dilute in methanol.

Answer 83

less number of trays are required.

Question 84

The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law. * exponential * parabolic * linear * cubic

Answer 84

exponential

Question 85

Which of the following binary systems is an example of a maximum boiling azeotrope ? * Water-hydrochloric acid. * Acetone-carbon disulphide. * Water-ethyl alcohol. * n-heptane-n-octane.

Answer 85

Water-hydrochloric acid.

Question 86

(NRe . NSc) is termed in mass transfer operation as the __________ number. * Stanton * Sherwood * Peclet * none of these

Answer 86

Peclet

Question 87

The binary diffusivity in gases and liquids vary respectively as * T^3/2 and T * T and T^3/2 * (T)^1/2 and T^3/2/ * T^3/2 and (T)^1/2

Answer 87

T^3/2 and T

Question 88

Pick out the correct statement. * The slope of the stripping line is always less than unity. * For a given separation in a binary distillation column, with increase in reflux ratio (above the minimum reflux ratio), the fixed cost of the distillation column first increases and then decreases. * In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux. * Kremsor-Brown-Souder's equation is used to calculate the efficiency of a plate tower.

Answer 88

In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux. true ans: Kremsor-Brown-Souder's equation is used to calculate the efficiency of a plate tower.

Question 89

Pick out the correct statement. * Dialysis process is used for the production of fresh water from brine. * Electrodylsis is used in the manufacture of NaOH. * Electrodylsis is used for the refin-ning/purification of petrol. * both (b) and (c).

Answer 89

Electrodylsis is used in the manufacture of NaOH. true ans: there is no correct statement

Question 90

Pick out the correct statement. * Bound moisture is removed during constant rate drying period. * Free moisture is removed during falling rate drying period. * The sum of free moisture and equilibrium moisture in a solid is called the critical moisture. * The driving force for mass transfer in a wet solid is its free moisture content.

Answer 90

The driving force for mass transfer in a wet solid is its free moisture content.

Question 91

Very tall packed towers are divided into series of beds to * reduce the overall pressure drop * avoid channelling * reduce liquid hold-up * avoid flooding

Answer 91

avoid channelling

Question 92

Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture. * unbound * free * critical * bound

Answer 92

free

Question 93

With increase in temperature, the solubility of gases in liquids, at fixed pressure * increases * decreases * remains same * either (a) or (b), depends on the system

Answer 93

decreases

Question 94

In most of the vacuum crystalliser, vacuum is generally produced by means of a * suction pump * compressed air jet * steam jet ejector with a barometric condenser * none of these

Answer 94

steam jet ejector with a barometric condenser

Question 95

On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in * greater degree of separation with a fixed number of trays * increased reboiler load * increased reflux ratio * None of these.

Answer 95

increased reflux ratio

Question 96

__________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids. * Watted wall * Packed * Plate * Spray

Answer 96

Plate

Question 97

Deairation (removal of O2) of water is done by * rectification * absorption * ion-exchange * adsorption

Answer 97

ion-exchange

Question 98

Make up water is supplied during cooling tower operation to compensate for water losses due to * evaporation * blowdown * entrainment * all (a), (b)&(c)

Answer 98

all (a), (b)&(c)

Question 99

Pick out the wrong statement. * The mole fraction of solute is directly proportional to the molality of a 'dilute' solution. * For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is nonlinear in the case of steady state unimolal unidirectional diffusion. * Azeotropes obey Raoult's law at all temperature. * The relative volatility of a binary mixture at the azeotropic composition is 1.

Answer 99

Azeotropes obey Raoult's law at all temperature.

Question 100

A minimum boiling azeotrope is exemplified by * toluene-benzene * acetone-carbon disulphide * water-isobutyl alcohol * none of these

Answer 100

acetone-carbon disulphide

Question 101

Which of the following solutions will follow Raoult's law most closely ? * A solution of benzene, toluene and oxylene. * 35% solution of camphor in water. * 35% solution of NH3 in water. * A solution of polar organic compounds (not of homologs of a series).

Answer 101

A solution of benzene, toluene and oxylene.

Question 102

Use of raschig rings in place of crushed stones as packing in packed beds (other things being same) * increases pressure drop, increases surface area. * increases pressure drop, decreases surface area. * decreases pressure drop, increases surface area. * decreases pressure drop, decreases surface area.

Answer 102

decreases pressure drop, increases surface area.

Question 103

The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are * parallel * straight * both parallel and straight * neither parallel nor straight

Answer 103

both parallel and straight

Question 104

As complete saturation of an adsorbent is approached, the differential heat of adsorption approaches * that of normal condensation. * integral heat of adsorption. * zero. * none of these.

Answer 104

that of normal condensation.

Question 105

'Absorption with chemical reaction' is involved in the removal of * carbon dioxide from gaseous stream using alkaline solution. * benzol from coke oven gas using solar oil/wash oil. * ammonia from coke oven gas using refrigerated water. * tar from coke oven gas in primary gas coolers using chilled water.

Answer 105

carbon dioxide from gaseous stream using alkaline solution.

Question 106

The-relative volatility for separation of a non-ideal binary mixture by distillation should be * 0 * 1 * > 1 * < 1

Answer 106

> 1

Question 107

Pick out the wrong statement: * Reboiler is not used in open steam distillation. * The separation of solutes of different molecular sizes in a liquid solution by use of a suitable membrane is called dialysis. * Freeze drying is used for the drying of fish. * Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.

Answer 107

Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.

Question 108

In paper industry, paper is dried in a __________ dryer. * tunnel * heated cylinder * conveyor * festoon

Answer 108

heated cylinder

Question 109

Pick out the wrong statement. - Critical moisture content is not a property of the material itself. - A sharp increase in pressure drop gives an indication of the flooding in a distillation column. - Separation of components is not possible in liquid extraction, if selectivity is unity. - Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.

Answer 109

Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.

Question 110

Only small amount of evaporation of water produces large cooling effects because of its * large latent heat * low viscosity * small latent heat * none of these

Answer 110

large latent heat

Question 111

The most common packing used in industrial operations is __________ rings. * raschig * lessing * cross-partition * single spiral

Answer 111

raschig

Question 112

When the feed to a distillation column is a saturated liquid, slope of the feed line is * zero * unity * infinity * none of these

Answer 112

infinity

Question 113

Leaching of sugar from sugar beets is done by * hot water * hexane * dilute H2SO4 * lime water

Answer 113

hot water

Question 114

Absorption factor method is used to calculate the number of ideal stages, when * operating line lies above the equilibrium line. * operating line lies below the equilibrium line. * both operating and equilibrium lines are parallel. * pressure drop in the column is very high.

Answer 114

both operating and equilibrium lines are parallel.

Question 115

Flights in a rotary dryer are provided to * lift and shower the solids thus exposing it thoroughly to the drying action of the gas. * reduce the residence time of solid. * increase the residence time of the solid. * none of these.

Answer 115

lift and shower the solids thus exposing it thoroughly to the drying action of the gas.

Question 116

If f = moles of vapour present per mole of feed, then the slope of feed line is (Mcabe-Thiele method) * (1-f)/f * - (f-1)/f * -1/f * -f/(1-f)

Answer 116

* -1/f

Question 117

If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that * the system comprises of partially mis-cible liquids. * the system comprises of miscible liquids. * the system comprises of an azeotrope. * on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.

Answer 117

on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.

Question 118

The rate of mass transfer is not dependent upon the * degree of dispersion of one fluid in the other. * interfacial surface exposed between the phases. * both (a) & (b). * none of these.

Answer 118

none of these.

Question 119

At equilibrium the concentration of water in vapour phase (C*)in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is * 0.0 * 0.2 * 0.4 * 1.0

Answer 119

0.4

Question 120

For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around * 0.60 * 0.24 * 1 * 0.72

Answer 120

1

Question 121

The reciprocal of stripping factor is termed as * selectivity index * relative volatility * absorption factor * Murphree efficiency

Answer 121

absorption factor

Question 122

Ponchan-Savarit method analyses the fractional equipment based on * enthalpy balance only. * material balance only. * both enthalpy and material balances. * the assumption of constant molaloverflow.

Answer 122

both enthalpy and material balances.

Question 123

The binary diffusivity in gases at atmospheric conditions is about * 10^-9 cm/sec * 10^-1 cm^2/sec * 10^-3 sec/cm * 10^-4 cm^2/sec^2

Answer 123

10^-1 cm^2/sec

Question 124

Percentage saturation is __________ the relative saturation. * always smaller than * always greater than * not related to * none of these

Answer 124

always smaller than

Question 125

In case of a desorber (stripper), the * operating line always lies above the equilibrium curve. * operating line always lies below the equilibrium curve. * temperature remains unaffected. * temperature always increases.

Answer 125

operating line always lies below the equilibrium curve.

Question 126

What is the reflux ratio at total reflux ? * Zero * Infinity * Unity * Data insufficient

Answer 126

Infinity

Question 127

Under conditions of flooding in packed tower, the gas pressure drop * decreases rapidly * increases rapidly * remains constant * is maximum

Answer 127

is maximum

Question 128

For achieving rapid drying rate in a spray dryer, the diameter of the particles in the feed should be in the range of __________ microns (1 mm = 1000 microns). * 1-5 * 10-60 * 200-300 * > 500

Answer 128

10-60

Question 129

For absorbing a sparingly soluble gas in a liquid * gas side mass transfer co-efficient should be increased. * liquid side mass transfer co-efficient should be increased. * liquid side mass transfer co-efficient should be decreased. * mass transfer co-efficient must be kept constant.

Answer 129

liquid side mass transfer co-efficient should be increased.

Question 130

The change in enthalpy per unit weight of adsorbed gas when adsorbed on gas free or "outgassed" adsorbent to from a definite concentration of adsorbate is called its * integral heat of adsorption. * heat of wetting. * differential heat of adsorption. * heat of normal condensation.

Answer 130

integral heat of adsorption.

Question 131

The minimum number of theoretical plates is required for achieving a given separation in distillation column with * no reflux * total reflux * zero reflux ratio * minimum reflux ratio

Answer 131

total reflux

Question 132

A good solvent used for absorption should not have very high * viscosity * vapor pressure * freezing point * all (a), (b) & (c)

Answer 132

all (a), (b) & (c)

Question 133

In a counter-current liquid extractor * both liquids flow at fixed rate. * both liquids can have any desired flow rate. * only one of the liquids may be pumped at any desired rate. * liquid's flow rate depends upon the temperature and pressure.

Answer 133

only one of the liquids may be pumped at any desired rate.

Question 134

Which of the following is an undesirable property for an absorbing solvent ? * Low vapour pressure * Low velocity * Low freezing point * None of these

Answer 134

None of these

Question 135

The wetted wall tower is used to determine * individual mass transfer co-efficient (M.T.C.) in gaseous system. * M.T.C. of individual components in a liquid-liquid system. * M.T.C. of liquid in liquid-gas system. * the overall M.T.C. of the system.

Answer 135

individual mass transfer co-efficient (M.T.C.) in gaseous system.

Question 136

Weight of 1 m^3 of humid air as compared to 1 m^3 of dry air, under the same conditions, is * less * more * same * unpredictable

Answer 136

less

Question 137

Positive deviation from Raoult's law means a mixture whose total pressure is * greater than that computed for ideality. * less than that computed for ideality. * less than the sum of the vapour pressure of the components. * none of these.

Answer 137

greater than that computed for ideality.

Question 138

With increase in gas rate, the number of transfer units, NtoG, for a fixed degree of absorption by a fixed amount of solvent * increases * decreases * decreases linearly * remains unaffected

Answer 138

increases

Question 139

Schmidt number is given by * μ/ρ.DAB * Re.Pe * Sh x Pe * Re/Pe

Answer 139

μ/ρ.DAB

Question 140

Prandtl number for water at 20°C is about 7 70 0.7 150.

Answer 140

7

Question 141

Boiling point diagram is * not affected by pressure. * affected by pressure. * a plot of temperature vs. liquid composition. * a plot of temperature vs. vapour composition.

Answer 141

affected by pressure.

Question 142

When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30°C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system, * as the acetone concentration increases, the solubility curves approach each other. * both the phases become identical at a particular common point on both the solubility curves called the plait point. * the distribution curve which is a plot between x (acetone concentration in one phase) and y (acetone concentration in other phase) is analogous to x-y curve used in distillation and absorption terminates on the x = y diagonal at the concentration of the plait point. * all (a), (b) and (c).

Answer 142

all (a), (b) and (c).

Question 143

Steam distillation is used to * reduce the number of plates. * avoid thermal decomposition of a component. * increase the efficiency of separation. * increase the total pressure of distillation.

Answer 143

avoid thermal decomposition of a component.

Question 144

Freundlich equation applies to the adsorption of solute from * dilute solutions, over a small concentration range. * gaseous solutions at high pressure. * concentrated solutions. * none of these.

Answer 144

dilute solutions, over a small concentration range.

Question 145

For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement. * no change in theoretical * marginal decrease in the number of * major decrease in the number of * none of these

Answer 145

marginal decrease in the number of

Question 146

The apex of an equilateral-triangular coordinate (in ternary liquid system) represents a/an * pure component * binary mixture * ternary mixture * insoluble binary system

Answer 146

pure component

Question 147

The diffusivity (D) in a binary gas mixture is related to the pressure (P) as * D ∝ P^0.5 * D ∝ 1/p^0.5 * D ∝ 1/p * D ∝ 1/p^1.5

Answer 147

D ∝ 1/p

Question 148

A slurry is to be dried to produce flaky solid. Which dryer would you recommend ? * Spray dryer * Drum dryer * Rotary dryer * Dielectric dryer

Answer 148

Spray dryer

Question 149

Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent ? * Cooling and dehumidification. * Heating and dehumidification at almost constant wet bulb temperature. * Dehumidification with dry bulb temperature remaining constant. * None of these.

Answer 149

Heating and dehumidification at almost constant wet bulb temperature.

Question 150

In gas-liquid contact operation, the number of ideal stages, . This is true when the stripping factor 'S' is * S > 1 * S < 1 * S = 1 * S = ∞

Answer 150

S > 1

Question 151

The cooling effect in a cooling tower can not be increased by * increasing the air velocity over the wet surfaces. * reducing the humidity of entering air. * lowering the barometric pressure. * none of these.

Answer 151

none of these.

Question 152

The value of NA/(NA + NB) for steady state molecular diffusion of gas 'A' through non-diffusing gas 'B' is * 1 * ∞ * 0.5 * 2

Answer 152

1

Question 153

Pick out the wrong statement * Co-current absorbers are usually used, when the gas to be dissolved in the liquid is a pure substance. * In case of gas absorption, HETP is equal to HTU, when both the operating line & the equilibrium lines are parallel. * Hatta number is important in case of gas absorption with chemical reaction. * In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.

Answer 153

In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.

Question 154

When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation. * continuous * steam * azerotropic * none of these

Answer 154

steam

Question 155

Large scale drying of wheat is done in a __________ dryer. * fluidised bed * spouted bed * tray * vacuum rotary

Answer 155

spouted bed

Question 156

Azeotropic distillation is employed to separate * constant boiling mixture. * high boiling mixture. * mixture with very high relative volatility. * heat sensitive materials.

Answer 156

constant boiling mixture.

Question 157

The drying time between fixed moisture content within diffusion controlled 'falling rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid ) * T^1/2 * T * T^2 * T^3

Answer 157

T^2

Question 158

At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes * 1 * 0 * ∞ * none of these

Answer 158

∞

Question 159

Pressure drop through plate tower as compared to that through packed tower, for the same duty will be * less * more * equal * either (a) or (b); depends on the packing height

Answer 159

more

Question 160

Dimension of mass diffusivity is the same as that of * kinematic viscosity * dynamic viscosity * surface tension * pressure

Answer 160

kinematic viscosity

Question 161

Dorr thickener is an equipment used for * classification * sedimentation * clarification * leaching

Answer 161

sedimentation

Question 162

Steam distillation is used to separate * azeotropes. * high boiling substances from nonvolatile impurities. * heat sensitive materials. * mixtures of low relative volatility.

Answer 162

high boiling substances from nonvolatile impurities.

Question 163

In distillation where q is defined as the moles of liquid flow in the stripping section per mole of feed introduced, for saturated liquid feed * q > 1 * q < 1 * q = 1 * q = 0

Answer 163

q = 1

Question 164

Which of the following is an undesirable property in a tower packing ? * Large surface per unit volume. * Large free cross-section. * Low weight per unit volume. * Large weight of liquid retained.

Answer 164

Large weight of liquid retained.

Question 165

Water entrained by circulating air in cooling towers is termed as * drift * blow down * vapor load * none of these.

Answer 165

drift

Question 166

A 25 cm x 25 cm x 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m x 1m x 1cm flat sheet of the same material is to be dried from one side only.Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is * 1000 * 1500 * 2000 * 2500

Answer 166

1000

Question 167

With increase in temperature, the rate of leaching increases, because the * diffusivity of solute increases. * viscosity of solvent decreases. * thermal conductivity of solute increases. * none of these.

Answer 167

diffusivity of solute increases.

Question 168

Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity. * molal * relative * percentage * none of these

Answer 168

molal

Question 169

The Knudsen diffusivity is proportional to (where, T = absolute temperature) * T^1/2 * T^2 * T * T^4

Answer 169

T^1/2

Question 170

In an absorption coloumn, the flooding velocity for random packing is __________ that for stacked/regular packing. * greater than * smaller than * equal to * either (a), or (b) ; depends on the type of packing

Answer 170

smaller than

Question 171

The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.) * Kc = Kp = Km * Kc = Kp/RT = Km . RT/P * Kc = Kp . RT = Km . RT/p * none of these

Answer 171

Kc = Kp . RT = Km . RT/p

Question 172

Leaching of uranium ore and gold ore is done in * centrifugal extractor * Pachuka tanks * Bollman extractor * none of these

Answer 172

Pachuka tanks

Question 173

Blowdown in a cooling tower * means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities. * increases the scale forming tendencies of water. * is undesirable. * all (a), (b) & (c).

Answer 173

means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.

Question 174

Antibiotics are best handled in a * Podbielniak extractor. * sieve tray contractor. * rotating disc contactor. * pulsed column extractor.

Answer 174

Podbielniak extractor.

Question 175

The fixed cost of a distillation column at minimum reflux ratio is * minimum * infinite * optimum * none of these

Answer 175

infinite

Question 176

__________ extractor uses centrifugal force for separating the two phases. * Treybal * Schiebel * Podbielniak * None of these

Answer 176

Podbielniak

Question 177

In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of * 1.5 * -0.6 * -1.5 * 0.6

Answer 177

-1.5

Question 178

Pick out the wrong statement. * Mechanical agitation is required, if the system has low interfacial tension. * Seive tray towers are generally used for systems having low interfacial tension. * When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance. * Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar and turbulent layers.

Answer 178

Mechanical agitation is required, if the system has low interfacial tension.

Question 179

Acetic acid will be most economically separated from a dilute solution of acetic acid in water by * solvent extraction * continuous distillation * evaporation * absorption

Answer 179

solvent extraction

Question 180

Design calculation for multiple component distillation is done by * Ponchon-Savarit method * Mccabe-Thiele method * enthalpy concentration method * tray to tray calculations.

Answer 180

tray to tray calculations.

Question 181

To get high tray efficiency * interfacial surface between liquid and gas phase should be large. * time of contact between the two phases should be less. * gas velocity should be very low. * liquid entrainment should be severe.

Answer 181

interfacial surface between liquid and gas phase should be large.

Question 182

The mass transfer co-efficient for a solid sphere of radius 'a' dissolving in a large volume of quiescent liquid, in which D is the diffusivity of solute, is * D/a * D/2a * proportional to D^1/2 * dependent on the Reynolds number

Answer 182

dependent on the Reynolds number

Question 183

Pick out the wrong statement. Generally for physical adsorption, a gas of * higher molecular weight is adsorbed in preference to a gas of low molecular weight. * high critical temperature is adsorbed in preference to a gas of low critical temperature. * low volatility is adsorbed in preference to a gas of high volatility. * none of these.

Answer 183

none of these.

Question 184

In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in * reducing the axial mixing. * increasing the rate of extraction. * maintaining the concentration difference between the two phases. * all 'a', 'b' & 'c'.

Answer 184

all 'a', 'b' & 'c'.

Question 185

In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as * KG = 1/KG + m/KL * 1/KG = 1/KG + m/KL * 1/KG = 1/KL + m/KG * KG = 1/K/l + m/KG

Answer 185

1/KG = 1/KG + m/KL

Question 186

Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when * extracting solvent is cheaply & abundantly available. * one of the liquid components is heat sensitive. * viscosity of liquid components is very high. * one of the liquid components has very high affinity towards the solvent.

Answer 186

one of the liquid components has very high affinity towards the solvent.

Question 187

Inside the distillation column, the * driving force for the vapour flow is the pressure drop. * liquids are not always at their bubble points. * pressure increases gradually from bottom to the top of the column. * none of these

Answer 187

driving force for the vapour flow is the pressure drop.

Question 188

Occurrence of 'case hardening' during drying of a high moisture solid cake __________ the drying rate. * increases * decreases * does not affect * exponentially increases

Answer 188

decreases

Question 189

Which of the following is not a continuous drier ? * Drum drier * Spray drier * Tunnel drier * Tray drier

Answer 189

Tray drier

Question 190

Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is * insoluble in the liquid * soluble in the liquid * non-ideal in nature * at a fixed temperature

Answer 190

insoluble in the liquid

Question 191

__________ is the temperature at which a gas-vapor mixture becomes saturated, when cooled at constant total pressure out of contact with a liquid. * Dew point * Bubble point * Dry bulb temperature * Wet bulb temperature

Answer 191

Dew point

Question 192

Rate of leaching increases with increasing * temperature * viscosity of solvent * pressure * size of the solid

Answer 192

temperature

Question 193

An azeotropic mixture is a __________ mixture. * binary * ternary * constant boiling point * none of these

Answer 193

constant boiling point

Question 194

Pick out the wrong statement. * In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed. * In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency. * For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10^-2 m/s. Then the average mass transfer co-efficient for the plate is 2 x 10^-2 m/s. * The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity.

Answer 194

For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10^-2 m/s. Then the average mass transfer co-efficient for the plate is 2 x 10^-2 m/s.

Question 195

Molecular seives are regenerated by heating to __________ °C. * < 150 * 200-330 * > 500 * > 1000

Answer 195

200-330

Question 196

In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as * Ri = Re / 1-Re * Ri = 1-Re/ Re * Ri = Re * Ri = Re/ 1+Re

Answer 196

Ri = Re/ 1+Re

Question 197

In a counter-current extractor, as the axial mixing increases, the extraction efficiency * increases * decreases * remains unchanged * depends on the pressure of the system

Answer 197

decreases

Question 198

Heat sensitive materials like certain pharmaceuticals and food stuffs can be dried in a/an __________ dryer. * indirect tray * spray * freeze * none of these

Answer 198

freeze

Question 199

In extractive distillation, solvent is * added to alter the relative volatility of the mixture. * of high volatility. * present in overhead stream. * of high viscosity to give high tray efficiency.

Answer 199

added to alter the relative volatility of the mixture.

Question 200

Radioactive nuclear waste is treated in * mixer-settler extractor * rotating-disc contactor * pulsed column extractor * Bollman extractor

Answer 200

pulsed column extractor

Question 201

Large scale drying of sugar is done in a __________ dryer. * spouted bed * tray * rotary * truck

Answer 201

rotary

Question 202

__________ temperature is the steady state temperature attained by a small amount of liquid evaporating into a large quantity of unsaturated gas-vapor mixture. * Dry bulb * Wet bulb * Dew point * none of these

Answer 202

Wet bulb

Question 203

The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid ) * T^1/2 * T * T^1.5 * T^3

Answer 203

T

Question 204

__________ equation applies to diffusivities in liquids. * Gilliland * Hirschfelder * Wilke and Chang * none of these

Answer 204

Gilliland

Question 205

A packed tower compared to a plate tower for a particular mass transfer operation * incurs smaller pressure drop. * allows installation of cooling coils. * is less costly when built in large sizes/diameters. * is more suitable, if suspended solids are present in fluid streams.

Answer 205

incurs smaller pressure drop.

Question 206

Which of the following is the most commonly used leaching solvent in vegetable oil industry ? * Phenol * Hexane * Furfurol * Liquid SO2

Answer 206

Hexane

Question 207

In an absorber, HETP does not vary with the * flow rate of liquid * flow rate of gas * type and size of packing * none of these

Answer 207

none of these

Question 208

Large quantity of silica gel is normally dried in a __________ dryer. * freeze * through circulation * rotary vacuum * tray

Answer 208

through circulation

Question 209

For the same system, if the same liquid used in an absorber is decreased, the tower height will * increase * decrease * remain unaffected * decrease or increase ; depends on the type of liquid

Answer 209

increase

Question 210

Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant. * agitated vessel * sieve tray column * bubble cap column * packed tower

Answer 210

agitated vessel

Question 211

Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent * a pure component. * a binary mixture. * a ternary mixture. * partially miscible ternary system.

Answer 211

a binary mixture.

Question 212

In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when * saturated feed is not used. * an azeotrope forms. * the latent heat of vaporisation of the more and less volatile components are greatly different. * a total condenser is used.

Answer 212

a total condenser is used.

Question 213

In an interphase mass transfer process, the lesser the solubility of a given solute in a liquid, the higher are the chances that the transfer process will be * liquid phase resistance-controlled. * gas phase resistance controlled. * impossible. * driven by a non-linear driving force.

Answer 213

gas phase resistance controlled.

Question 214

As the reflux ratio decreases, the * separation becomes more efficient. * number of plates increases. * column diameter increases. * none of these.

Answer 214

number of plates increases.

Question 215

Which of the following equipments is not used for gas dispersion ? * Agitated vessels * Bubble cap tray towers * Perforated sieve tray towers * Spray towers

Answer 215

Spray towers

Question 216

One mole feed of a binary mixture of a given composition is flash vaporised at a fixed P and T. If Raoult's law is obeyed, then changing the feed composition would effect * the product composition but not the fraction vaporised. * the product composition as well as the fraction vaporised. * the fraction vaporised but not the product composition. * neither the product composition nor the fraction vaporised.

Answer 216

the fraction vaporised but not the product composition.

Question 217

The equation, NA = DAB. Pt / RTZ is for * steady state equimolar counter diffusion * Fick's first law of diffusion * steady state diffusion for stagnant case * liquid M.T.C. by penetration theory.

Answer 217

steady state equimolar counter diffusion

Question 218

With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop * decreases * remains unchanged * increases * decreases exponentially

Answer 218

increases

Question 219

The equation, Na = (DAB.Pt / RTZ.PBM)(PA1 - PA2) is for * Fick's second law of diffusion. * steady state diffusion for stagnant case. * liquid M.T.C. by Higbie penetration theory. * none of these.

Answer 219

steady state diffusion for stagnant case.

Question 220

Which of these columns incurs the lowest pressure drop ? * Packed column (with stacked packing) * Packed column (with dumped packing) * Bubble plate column * Pulse column

Answer 220

Packed column (with stacked packing)

Question 221

In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase. * gas * liquid * both (a) & (b) * neither (a) nor (b)

Answer 221

liquid

Question 222

If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is * L/G * G/L * always < 1 * none of these

Answer 222

L/G

Question 223

Which of the following remains constant during evaporative cooling process with recirculated water supply ? * Relative humidity * Partial pressure of vapour * Wet bulb temperature * None of these

Answer 223

Wet bulb temperature

Question 224

For stripping of a gas in a counter current stripper, the operating line * lies above the equilibrium curve. * lies below the equilibrium curve. * can lie above or below the equilibrium curve. * is always parallel to the equilibrium curve.

Answer 224

can lie above or below the equilibrium curve.

Question 225

Which of the following same diameter columns gives lowest pressure drop per unit height ? * Bubble-cap column * Sieve-plate column * Packed column (stacked) * Randomly packed column

Answer 225

Packed column (stacked)

Question 226

Operating velocity in a packed tower is usually __________ the flooding velocity. * half * twice * equal to * more than

Answer 226

half

Question 227

The Knudsen diffusivity is dependent on the * molecular velocity only. * pore radius of the catalyst only. * molecular mean free path only. * molecular velocity and pore radius of the catalyst.

Answer 227

molecular velocity and pore radius of the catalyst.

Question 228

Minimum possible diameter of a packed coloumn is decided mainly by the * flooding * gas viscosity * liquid density * liquid hold up

Answer 228

flooding

Question 229

Solvent used in extractive distillation * is of low volatility. * forms a low boiling azeotrope. * forms a high boiling azeotrope. * does not alter the relative volatility of the original components.

Answer 229

forms a low boiling azeotrope.

Question 230

The cooling effect in a cooling tower can be speeded up by * increasing the air velocity and area of exposed wet surface. * reducing the barometric pressure. * reducing the humidity of the air. * all (a), (b) and (c).

Answer 230

all (a), (b) and (c).

Question 231

The following plot gives the saturated humidity (He) versus temperature (T).Line joining (H1, T1) and (H2, T2) is the constant enthalpy line. Choose the correct one from among the alternatives A, B, C and D. * T1-Dew point temp; T2-Dry bulb temp; T3-Wet bulb temp. * T1-Dew point temp; T2-Wet bulb temp; T3-Dry bulb temp. * T1-Wet bulb temp; T2-Dry bulb temp; T3-Dew point temp. * T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.

Answer 231

T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.

Question 232

When both the fluids flow concurrently in an absorber, the slope of the operating line is * -ve * +ve * 1 * -1

Answer 232

-ve

Question 233

The percentage humidity is less than the relative humidity only at __________ percent humidity. * zero * hundred * both zero and hundred * none of these

Answer 233

both zero and hundred

Question 234

Back-trapping in a distillation column * increases tray efficiency. * decreases tray efficiency. * reduces pressure drop. * is desirable, as it provides improved vapour-liquid contact.

Answer 234

decreases tray efficiency.

Question 235

Flooding in a vapor-liquid contacting equipment occurs in a tray, when the pressure drop through a tray is __________ the liquid head available in the downcomer. * less than * more than * same as * very much less

Answer 235

more than

Question 236

Milk is dried usually in a __________ dryer. * freeze * spray * tray * rotary

Answer 236

spray

Question 237

At a given equilibrium pressure, with increase in temperature, the concentration of adsorbed gas on solid adsorbant * increases * decreases * remains unchanged * increases exponentially

Answer 237

decreases

Question 238

Which of the following adsorbent is used to decolourise yellow glycerine ? * Silica gel * Alumina * Fuller's earth * Activated carbon

Answer 238

Activated carbon

Question 239

Which of the following liquid temperature (T) Vs. vapor-gas mixture enthalpy (H) diagram is valid for humidification operation?

Answer 239

Question 240

In a distillation column, with increase in the reflux ratio, the heat removed in the cooler * increases. * decreases. * remains unaffected. * and the heat required in reboiler decreases.

Answer 240

increases.

Question 241

Pick out the wrong statement. * Constant pressure distillation can not separate an azeotropic mixture. * Relative volatility of a binary mixture changes appreciably with the minor change in temperature. * The relative volatility of a binary mixture at azeotropic composition is unity. * Flash distillation is practised on wide spread scale in petroleum refinery.

Answer 241

Relative volatility of a binary mixture changes appreciably with the minor change in temperature.

Question 242

Which of the following is not a unit of mass transfer co-efficient ? * moles transferred / (time)(area)(mole fraction) * moles transferred / (time)(area)(pressure) * moles transferred / (time)(area)(massA/massB) * none of these

Answer 242

none of these

Question 243

The falling rate period in the drying of a solid is characterised by * increase in rate of drying. * increasing temperatures both on the surface and within the solid. * decreasing temperatures. * none of these.

Answer 243

increasing temperatures both on the surface and within the solid.

Question 244

In which of the following unit operations, the selectivity is an important parameter ? * Distillation * Solvent extraction * Absorption * None of these

Answer 244

Solvent extraction

Question 245

Which of the following is an undesirable characteristic for the solvent used in gas absorption ? * Low vapor pressure * Low viscosity * High gas solubility * None of these

Answer 245

None of these

Question 246

Which of the following equipments is not used for liquid dispersion ? * Wetted wall towers * Packed towers * Venturi scrubbers * Agitated vessels

Answer 246

Agitated vessels

Question 247

Diameter of raschig rings used in packed tower in industry is normally around __________ inches. * 2 * 8 * 12 * 18

Answer 247

2

Question 248

The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is * 2.09 x 10^-4 * 2.09 x 10^-5 * 2.09 x 10^-9 * 2.09 x 10^-12

Answer 248

2.09 x 10^-9

Question 249

Pick out the wrong statement. * The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one. * Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference. * According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by (DAB)^1/2 (b)P - 3, Q - 2 * The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz.

Answer 249

According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by (DAB)^1/2 (b)P - 3, Q - 2

Question 250

In case of non-ideal gases and liquids, the molal diffusivity * varies inversely as the pressure. * varies directly as the pressure. * is independent of pressure. * is equal to the volumetric diffusivity.

Answer 250

is independent of pressure.

Question 251

Condensation of a vapour-gas mixture just begins, when (where, p = partial pressure of the vapour P = vapour pressure of the liquid ) * p = P * p >>P * p < P * p << P

Answer 251

p = P

Question 252

__________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower. * Sherwood * Stanton * Lewis * Peclet

Answer 252

Lewis

Question 253

The expression, y(1 - x)/x(1 - y) is for * absorption factor * relative volatility * selectivity * Murphree efficiency

Answer 253

relative volatility

Question 254

In physical terms, Schmidt number means * thermal diffusivity/mass diffusivity. * thermal diffusivity/momentum diffusivity. * momentum diffusivity/mass diffusivity. * mass diffusivity/thermal diffusivity.

Answer 254

momentum diffusivity/mass diffusivity.

Question 255

In case of liquids, the binary diffusivity is proportional to (where, T = temperature) * T * T^1/2 * T^2 * 1/T

Answer 255

T

Question 256

The diffusivity, DAB (for component A diffusing in B) is equal to the diffusivity DBA (for component B diffusing in A) for a binary mixture of * Newtonion liquids * non-Newtonion liquids * ideal gases * real gases

Answer 256

ideal gases

Question 257

Mass transfer co-efficient is directly proportional to DAB0.5, according to __________ theory. * penetration * surface renewal * film * none of these

Answer 257

penetration

Question 258

Sand is dried in foundaries in a___drier. * rotary * fluidized bed * vacuum * spray

Answer 258

fluidized bed

Question 259

Which of the following employs an accessory known as 'drift eliminator' ? * Multiple effect evaporator. * Mechanical draft cooling tower. * Rotary dryer. * Rotating disc contactor.

Answer 259

Mechanical draft cooling tower.

Question 260

Pick out the correct statement. * Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas. * The 'Hatta number' is important in problems involving gas absorption without chemical reaction. * For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion. * Total reflux in case of distillation operation requires infinite number of plates for a binary system separation.

Answer 260

For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion.

Question 261

Pick out the correct statement. * For identical gas flow rates, less pressure drop occurs through a plate tower than through a packed tower. * Plate column can handle greater liquid loads without flooding than packed column, but the liquid hold up is more in the case of plate column. * For the same duty, plate columns weigh less than packed columns. * all (a), (b) and (c).

Answer 261

all (a), (b) and (c).

Question 262

Humid volume is the total volume in m3 of 1 kg of * vapour laden gas at 1 atm. and room temperature. * gas plus its accompanying vapour at 1 atm. and room temperature. * gas plus its accompanying vapour at 1 atm. and gas temperature. * vapour laden gas at 1 atm. and gas temperature.

Answer 262

gas plus its accompanying vapour at 1 atm. and gas temperature.

Question 263

Diameter to height ratio for a rashig ring is * 1 * 0.5 * 2 * 8

Answer 263

1

Question 264

The equipment used in the extraction of highly corrosive radio active liquids is * pulse column * spray column * mixer settler * baffle tower

Answer 264

pulse column

Question 265

Advantage of continuous drying over batch drying is that the * drying cost per unit weight of dried product is less. * product with more uniform moisture content is produced. * equipment size required is smaller. * all 'a', 'b' & 'c'

Answer 265

all 'a', 'b' & 'c'

Question 266

With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system) * increases * decreases * remains unaffected * increases Linearly

Answer 266

increases

Question 267

In a packed bed absorption column, the channelling will be noted by the * increase in flow rate. * sharp drop in pressure drop. * sharp rise in pressure drop. * none of these.

Answer 267

sharp drop in pressure drop.

Question 268

Gaseous diffusivity at atmospheric pressure is of the order of __________ cm^2/second. * 1 * 1 to 5 * 5 to 10 * > 10

Answer 268

1

Question 269

In liquid-liquid extraction, the number of phases at plait point is * 1 * 2 * 3 * 4

Answer 269

1

Question 270

In a liquid-liquid extraction, 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X, where Y* is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer. * The entire amount of C is transferred to solvent B. * Less than 2 kg but more than 1 kg of C is transferred to solvent B. * Less than 1 kg of C is transferred to B. * No amount of C is tranferred to B.

Answer 270

The entire amount of C is transferred to solvent B.

Question 271

The surface renewal frequency in Danckwerts' model of mass transfer is given by (KL: mass transfer co-efficient) * (KL^2.DA)^1/2 * KL^2.DA * KL^2/DA * KL/DA^2

Answer 271

(KL^2.DA)^1/2

Question 272

If Rm is the minimum reflux ratio, the optimum reflux ratio may be around __________ Rm. * 1.2 to 1.5 * 2.5 to 3 * 3 to 4 * 5

Answer 272

1.2 to 1.5

Question 273

During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant. * wet bulb temperature * partial pressure of water vapor * relative humidity * none of these

Answer 273

wet bulb temperature

Question 274

In case of absorption, both the operating and equilibrium lines will be straight for * isothermal operation. * dilute solutions. * dilute solutions and isothermal operation. * none of these.

Answer 274

dilute solutions and isothermal operation.

Question 275

Mass transfer co-efficient varies as DAB0.5, according to the __________ theory. * film * surface renewal * penetration * none of these

Answer 275

surface renewal

Question 276

For an absorber, both equilibrium and operating line will be straight for * concentrated solution and non-isothermal operation. * dilute solution and non-isothermal operation. * dilute solution and isothermal operation. * concentrated solution and isothermal operation.

Answer 276

dilute solution and isothermal operation.

Question 277

A distillation column separates 10000 kg/hr of a benzene-toluene mixture as shown in the figure below : In the figure xF, xD and xW represent the weight fraction of benzene in the feed, distillate and residue respectively. The reflux ratio is * 0.5 * 0.6 * 1.0 * 2.0

Answer 277

0.6

Question 278

Unsaturated air (with dry bulb and wet bulb temperatures being 45°C and 25°C respectively) is passed through a water spray chamber maintained at 23°C. The air will be cooled and * humidified with wet bulb temperature decreasing. * humidified at constant wet bulb temperature. * dehumidified. * none of these

Answer 278

humidified with wet bulb temperature decreasing.

Question 279

Humid volume, at a given temperature is a/an __________ function of humidity. * inverse * exponential * linear * logarithmic

Answer 279

linear

Question 280

The Schmidt number which is defined as, μ/ρ D, is the ratio of the * momentum diffusivity to the mass dif-fusivity. * thermal diffusivity to the mass diffusivity. * momentum diffusivity to the thermal diffusivity. * none of these.

Answer 280

momentum diffusivity to the mass dif-fusivity.

Question 281

If f is defined as above, then which of the following applies to a feed at dew point ? * f = 1 * f < 1 * f > 1 * 0 < f < 1

Answer 281

f = 1

Question 282

Perforated plate towers are unique for solvent extraction because, they provide * higher contact area. * better contact of the phase. * repeated coalescence & redispersion of the drop phase. * none of these.

Answer 282

repeated coalescence & redispersion of the drop phase.

Question 283

In case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of __________ is zero. * interface * gas phase * liquid phase * all 'a', 'b' & 'c'

Answer 283

interface

Question 284

Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations. * Sherwood number in mass transfer is analogous to Nusselt number in heat transfer. * Prandtl number in heat transfer is analogous to Schmidt number in mass transfer. * Reynolds number in mass transfer is analogous to Grashoff number in heat transfer. * Reynolds number remains the same in both heat and mass transfer.

Answer 284

Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.

Question 285

The slope of the operating line for a single component co-current absorber when plotted in terms of mole ratio units is * 0 * ∞ * -ve * +ve

Answer 285

-ve

Question 286

The individual mass transfer co-efficients (moles/m2 . s) for absorption of a solute from a gas mixture into a liquid solvent are, KL = 4.5 and KG = 1.5. The slope of the equilibrium line is 3. Which of the following resistance (s) is (are) controlling ? * liquid side * gas side * interfacial * both liquid and gas side

Answer 286

gas side

Question 287

Pore size of the molecular seive 5A is __________ mm. * 5 * 0.5 * 0.05 * 50

Answer 287

0.5

Question 288

Swenson-Walker crystalliser is a __________ unit * continuous * batch * semi-batch * cooling (adiabatic)-cum-evaporation

Answer 288

continuous

Question 289

According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (αAB = 2) does not change appreciably in the coloumn. * 5 * 9 * 12 * 28

Answer 289

12

Question 290

Absorption (liquid-gas system) with evolution of heat as compared to isothermal absorption results in * decreased solute solubility. * large minimum liquid to gas (L/G) ratio. * large number of trays. * all (a), (b) and (c).

Answer 290

all (a), (b) and (c).

Question 291

With increase in temperature, the mutual solubility of two liquids * increases * decreases * remains unchanged * decreases exponentially

Answer 291

increases

Question 292

Pick out the wrong statement. * In solvent extraction, the distribution co-efficient should be as large as possible for solvent economy. * With increase in pressure, the solubility of gases in solvent increases at a fixed temperature. * Decrease in Murphree plate efficiency is an indication of entrainment in distillation coloumn. * The capacity of a distillation coloumn is maximum at total reflux.

Answer 292

The capacity of a distillation coloumn is maximum at total reflux.

Question 293

The relative volatility of a binary mixture at the azeotropic composition is * 1 * > 1 * 0 * ∞

Answer 293

1

Question 294

Relative volatility varies with the concentration of component for an ideal solution. The relative volatity of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when - only vapor phase follows Raoult's law. - only liquid phase obeys Dalton's law. - liquid phase obeys Dalton's law and vapor phase obeys Raoult's law. - Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.

Answer 294

Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.

Question 295

Bound moisture is that liquid which exerts an equilibrium vapor pressure __________ that of the pure liquid at the given temperature. * less than * more than * equal to * either (o) or (b); depends on the solid

Answer 295

less than

Question 296

Lewis number (Le) is * Sc / Pr * Pr x St * Sh x Pr * St x Sh

Answer 296

Sc / Pr

Question 297

Which of the following is not a continuous leaching equipment ? * Pachuka tank * Kennedy extractor * Bollman extractor * Hydrocyclones

Answer 297

Pachuka tank

Question 298

__________ extractor is used for the concentration of radioactive nuclear waste. * Pulsed column * Seive plate * Mixer-settler * Ballman

Answer 298

Pulsed column

Question 299

Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture. * free * unbound * equilibrium * bound

Answer 299

equilibrium

Question 300

All moisture in a non-hygroscopic material is the __________ moisture. * free * equilibrium * unbound * bound

Answer 300

unbound

Question 301

Pick out the correct relationship. (where, Ri = internal reflux ratio Ro = external reflux ratio. ) * (1 + Ro) = Ro/Ri * (1 - Ro) = Ro/Ri * (1 + Ri) = Ro/Ri * (1 - Ri) = Ro/Ri

Answer 301

(1 + Ro) = Ro/Ri

Question 302

Separation of __________ employs gaseous diffusion process. * N2 and O2 from air * isotopes of uranium * isotopes of helium * SO2 and air

Answer 302

isotopes of uranium

Question 303

For water-ethanol system, the minimum reflux ratio * is computed from the slope of the upper operating line that is tangent to the equilibrium curve. * is computed from the intercept of the operating line. * cannot be computed. * is the optimum reflux ratio.

Answer 303

is computed from the slope of the upper operating line that is tangent to the equilibrium curve.

Question 304

The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m^2/m^3) * 500 * 1200 * 900 * 800

Answer 304

500

Question 305

Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysterisis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption. * lower than * higher than * same as * either same or higher than

Answer 305

lower than

Question 306

Experimental determination of __________ is done by wetted wall column method. * diffusion co-efficient * mass transfer co-efficient * NTU * none of these

Answer 306

mass transfer co-efficient

Question 307

Pick out the wrong statement: * Absorption factor is constant, when the equilibrium and operating lines are straight. * In case of a stripper, the equilibrium curve is always below the operating line. * In case of an absorber, the operating line is always above the equilibrium curve. * In the absorption of low solubility gases, the liquid film is the controlling resistance.

Answer 307

In case of a stripper, the equilibrium curve is always below the operating line.

Question 308

In liquid extraction, if the selectivity is unity, then * separation of the constituents is the most effective. * no separation will occur. * amount of solvent required will be minimum. * solvent flow rate should be very low.

Answer 308

no separation will occur.

Question 309

Paper industry employs __________ driers. * cylinder * rotary * spray * fluidised bed

Answer 309

cylinder

Question 310

Pick out the wrong statement pertaining to the cooling towers. * In case of induced draft cooling tower, the fan is placed at the top of the tower. * Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air. * A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low. * Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

Answer 310

Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

Question 311

Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 x 10^-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m^2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is * 5.6 x 10^-4 * 8.5 x 10^-4 * 5.6 x 10^-3 * 8.5 x 10^-3

Answer 311

8.5 x 10^-4

Question 312

Leaching of coarse solid lumps is also termed as * decoction * dissolution * percolation * agitation and settling

Answer 312

percolation

Question 313

The main reason for dividing a tall packed tower into series of small towers is to * minimise the overall pressure drop. * avoid flooding. * reduce liquid hold up. * avoid channeling.

Answer 313

avoid channeling.

Question 314

Co-current absorbers are usually used when the gas to be dissolved in the liquid is * sparingly soluble * highly soluble * a pure substance * a mixture

Answer 314

a pure substance

Question 315

At what percentage (by volume) of alcohol composition, it forms an azeotrope with water ? * 90 * 91.5 * 95 * 99

Answer 315

95

Question 316

Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ coloumn. * spray * packed * bubble cap plate * wetted wall

Answer 316

wetted wall

Question 317

With the lowering of equilibrium pressure, at a given temperature, the amount of adsorbate on the adsorbent * increases. * decreases. * remains same. * either (a) or (b), depends on the system.

Answer 317

decreases.

Question 318

Mass transfer co-efficient is defined as * Flux = Co-efficient/concentration difference. * Co-efficient = Flux/concentration difference. * Flux=concentration difference/co-effi-cient. * none of these.

Answer 318

Co-efficient = Flux/concentration difference.

Question 319

When an unsaturated air-water mixture is heated at constant pressure, then * the partial pressure of water vapour increases. * the specific humidity decreases. * The relative humidity increases. * the relative humidity decreases.

Answer 319

the relative humidity decreases.

Question 320

At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent. * 100 * 0 * 50 * between 0 and 100

Answer 320

0

Question 321

In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is - equal to the heat of formation of surface compound. - equal to the heat of wetting. - zero. - called integral heat of adsorption.

Answer 321

equal to the heat of wetting.

Question 322

Pick out the wrong statement: * Change in barometric pressure does not affect the relative humidity. * In case of a packed tower, the operating velocity is about half of the flooding velocity, generally. * 'Elution' means the desorption of the adsorbed solute by a solvent. * The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

Answer 322

The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

Question 323

The value of L/mG ratio for economical absorption operation ranges from * 0.5 to 0.8 * 0.8 to 1.2 * 1.25 to 2.0 * 2.5 to 3.5

Answer 323

1.25 to 2.0

Question 324

Large scale usage of flash distillation is practised in * soap manufacturing * ammonia synthesis plant * polymerisation industry * petroleum refinning

Answer 324

petroleum refinning

Question 325

High pressure at the bottom of a distillation tower handling heat sensitive materials results in * thermal decomposition of bottoms. * increased relative volatility. * erosion of the tower. * very efficient operation.

Answer 325

thermal decomposition of bottoms.

Question 326

Alcohol is dehydrated using __________ distillation. * extractive * azeotropic * steam * molecular

Answer 326

azeotropic

Question 327

Separation of two volatile liquids by distillation makes use of their * selectivity * relative volatility * solubility * density difference

Answer 327

relative volatility

Question 328

Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content. * rotary * tray * freeze * none of these

Answer 328

tray

Question 329

__________ is used as an 'entrainer' for the separation of acetic acid-water mixture by distillation. * Furfural * Benzol * Butyl acetate * Hexane

Answer 329

Butyl acetate

Question 330

Rotary dryers cannot handle __________ materials. * free flowing * dry * sticky * grannular

Answer 330

sticky

Question 331

Pick out the correct statement. * Diffusivity decreases with increase in temperature. * Diffusivity increases with increase in molecular weight. * Diffusivity increases with the size of the individual molecule. * none of these.

Answer 331

none of these.

Question 332

An example of elution is * separation of uranium oxide from its ore by H2SO4 in a Pachuca tank. * separation of sugar from sugar beet by hot water. * dissolution of tannin out of tree barks by water. * recovery of vegetable oils from seeds.

Answer 332

separation of uranium oxide from its ore by H2SO4 in a Pachuca tank.

Question 333

The operating line for an absorber is curved, when plotted in terms of * mole fractions * mole ratios * partial pressure * mass fractions

Answer 333

partial pressure

Question 334

Relative volatility does not change appreciably with the change in * temperature * vapour pressure of either component * total pressure * none of these

Answer 334

temperature

Question 335

The dew point of a saturated gas phase equals the __________ temperature. * gas * room * wet bulb * none of these

Answer 335

gas

Question 336

A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process ? * Flow rate of inlet air * Relative humidity of outlet air * Humidity of inlet air * Temperature of the solid

Answer 336

Temperature of the solid

Question 337

In case of liquid-liquid binary diffusion, diffusivity of one constituent into another is not dependent on the * temperature and pressure * concentration * nature of the constituents * none of these

Answer 337

none of these

Question 338

For continuous drying of grannular or crystalline material, the dryer used is the __________ dryer. * tunnel * tray * rotary * none of these

Answer 338

rotary

Question 339

When adsorption hysteresis is observed, the desorption equilibrium pressure is __________ that obtained by adsorption. * always lower than * always higher than * same as * dependent on the system; can be either lower or higher than

Answer 339

always lower than

Question 340

Moisture in a substance exerting an equilibrium vapour pressure less than that of pure liquid at the same temperature is called the __________ moisture. * bound * unbound * critical * none of these

Answer 340

bound

Question 341

For a binary mixture with low relative volatility, continuous rectification to get pure products will require * low reflux ratio * less number of trays * small cross-section column * high reflux ratio

Answer 341

high reflux ratio

Question 342

Detergent solution is dried to a powder in a * spray dryer * spouted bed dryer * tunnel dryer * pan open to atmosphere

Answer 342

spray dryer

Question 343

Which of the following mixtures does not form an azeotrope at atmosheric pressure? * Water-alcohol * Methyl alcohol-acetone * Butyl acetate-water * None of these

Answer 343

None of these

Question 344

During bottling of cold drinks (e.g. Pepsi), the main resistance to mass transfer for the absorption of carbon dioxide in water lies in the * gas film * liquid film * liquid-gas interface * none of these

Answer 344

liquid film

Question 345

The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by * increasing the gas film co-efficient. * increasing the liquid film co-efficient. * increasing the total pressure. * decreasing the total pressure.

Answer 345

increasing the gas film co-efficient.

Question 346

Flooding results in * high tray efficiency * low tray efficiency * high gas velocity * good contact between the fluids

Answer 346

low tray efficiency

Question 347

For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because * water has a high latent heat of evaporation. * Lewis number is close to unity. * they are always equal under all circumstances. * solubility of the components of air in water is very small.

Answer 347

water has a high latent heat of evaporation.

Question 348

In an operating distillation column, the * vapors and liquids are at their dew point and bubble point respectively * driving force for the liquid flow is its specific weight. * driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column. * highest temperature is encountered at the top of the column.

Answer 348

driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.

Question 349

The diffusivity (D) in a binary gas mixture is related to the temperature (T) as * D ∝ T * D ∝ T^0.5 * D ∝ T^1.5 * D ∝ T^2

Answer 349

D ∝ T^1.5

Question 350

For which of the following unit operations, Lewis number is of significance ? * Adsorption * Binary distillation * Gas absorption * Humidification

Answer 350

Humidification

Question 351

Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches. * 5 * 30 * 60 * 100

Answer 351

30

Question 352

If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement. * a1 = a2 * a1 = 2a2 * a1 = 0.5 a2 * none of these

Answer 352

none of these

Question 353

The dimension of diffusivity is same as that of the * density * molal concentration * kinematic viscosity * velocity head

Answer 353

kinematic viscosity

Question 354

The temperature to which a vapour gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature. * dew point * wet bulb * dry bulb * none of these

Answer 354

none of these

Question 355

Entrainer used in azeotropic distillation should * form a low boiling azeotrope with one of the constituents of the mixture. * form a new azeotrope of low relative volatility with one of the constituents of the mixture. * have high latent heat of vaporisation. * have high viscosity to provide high tray efficiency.

Answer 355

form a low boiling azeotrope with one of the constituents of the mixture.

Question 356

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because * temperature is less. * total pressure is less. * mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition. * saturated steam is used for steam distillation.

Answer 356

mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.

Question 357

Pick out the wrong statement. * The operating line always lies above the equilibrium solubility curve in case of a single component absorber. * The operating line always lies below the equilibrium solubility curve in case of a single component stripper. * The operating pressure in solvent extraction system should be below vapor pressures of all components. * The solubility of a particular gas in ideal solution in any solvent is always the same.

Answer 357

The operating pressure in solvent extraction system should be below vapor pressures of all components.

Question 358

Leaching of coffee from coffee beans is done by * hot water * hexane * lime water * dilute H2SO4 (hot)

Answer 358

hot water

Question 359

For contacting a highly soluble gas with a liquid * bubble the gas through liquid. * spray the liquid on gas stream. * either (a) or (b) would suffice. * none of these.

Answer 359

bubble the gas through liquid.

Question 360

During drying operation, it is easier to remove the __________ moisture. * equilibrium * critical * unbound * bound

Answer 360

unbound

Question 361

With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas * increases * decreases * decreases linearly * remains unaffected

Answer 361

decreases

Question 362

Ion exchange process is similar to * absorption * adsorption * extraction * leaching

Answer 362

adsorption

Question 363

Dryer widely used in a textile industry is __________ dryer. * festoon * cylinder * conveyor * tunnel

Answer 363

conveyor

Question 364

A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state, * composition of vapors and that of liquid do not vary throughout the column. * reboiler load and condenser load are minimum. * the top and bottom compositions are unchanged with and without total reflux. * the top and bottom compositions correspond to the maximum enrichment available.

Answer 364

the top and bottom compositions correspond to the maximum enrichment available.

Question 365

Solvent used in extractive distillation * changes the relative volatility of the original components. * should be of high volatility. * should form azeotropes with the original components. * all (a), (b) and (c)

Answer 365

changes the relative volatility of the original components.

Question 366

Air at a particular humidity is heated in a furnace. The new dew point * decreases * increases * depends on the extent of heating * remain unchanged

Answer 366

increases

Question 367

The vapour pressure exerted by the moisture contained in a wet solid depends upon the * nature of the moisture. * temperature. * nature of the solid. * all (a), (b) and (c).

Answer 367

all (a), (b) and (c).

Question 368

The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and, m = slope of the equilibrium line) * L/mG * G/mL * mL/G * LG/m

Answer 368

L/mG

Question 369

Smoke is an example of * solid dispersed in liquid * solid dispersed in gas * liquid dispersed in gas * gas dispersed in liquid

Answer 369

solid dispersed in gas

Question 370

Which of the following adsorbant is used in the refining of sugar ? * Bone charcoal * Wood charcoal * Silica gel * Activated clay

Answer 370

Bone charcoal

Question 371

In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at __________ reflux. * total * minimum * operating * maximum permissible

Answer 371

total

Question 372

Which of the following parameters remains constant during chemical dehumidifica-tion? * Dry bulb temperature * Partial pressure of vapour * Wet bulb temperature * None of these

Answer 372

Dry bulb temperature

Question 373

Drying of a solid involves __________ transfer. * only heat * only mass * both heat and mass * none of these

Answer 373

both heat and mass

Question 374

Mechanism of moisture removal in case of freeze drying of food stuff is by * evaporation * sublimation * dehydration * adsorption

Answer 374

sublimation

Question 375

The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture. * composition * temperature * total pressure * all (a), (b) and (c)

Answer 375

temperature

Question 376

Which is not concerned directly with mass transfer ? * Schmidt number * Sherwood number * Lewis relationship * Froude number

Answer 376

Froude number

Question 377

Removal of __________ exemplifies an adsorption unit operation. * uranium from its ore * water from petrol * ammonia from coke oven gas * mustard oil from mustard seed

Answer 377

water from petrol

Question 378

Can the efficiency of a plate in the distillation tower be greater than 100% ? * Yes * Normally not; but is possible if infinite number of plates are put. * Never * Yes ; if the reflux ratio is maximum.

Answer 378

Never

Question 379

With increase in the mass velocity of the gas, the rate of drying during the constant rate period __________ , if the conduction and radiation through the solid are negligible. * increases * decreases * remains same * increases linearly

Answer 379

increases

Question 380

For gas absorption, low viscosity solvents are preferred, because of their * better flow characteristics. * low pumping pressure drop. * rapid absorption rates. * all (a), (b) and (c).

Answer 380

all (a), (b) and (c).

Question 381

To remove all the moisture from a wet solid it requires exposure to __________ air. * perfectly dry * highly humid * high temperature * none of these

Answer 381

perfectly dry

Question 382

The operating cost of a distillation column at minimum reflux ratio is * minimum * maximum * infinite * zero

Answer 382

minimum

Question 383

The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is * 2 * 0.5 * 50 * 150

Answer 383

2

Question 384

Molecular diffusivity of a liquid * increases with temperature. * decreases with temperature. * may increase or decrease with temperature. * is independent of temperature.

Answer 384

increases with temperature.

Question 385

The wet and 'dry bulb temperature for a vapour-gas mixture are 25°C and 30°C respectively. If the mixture is heated to 45°C at constant pressure, the wet bulb temperature will be __________ °C. * 25 * > 25 * < 25 * - 25

Answer 385

* > 25

Question 386

Henry's law states that the * partial pressure of a component over a solution is proportional to its mole fraction in the liquid. * partial pressure of a component over a solution is proportional to the mole fraction in the vapour. * vapour pressure is equal to the product of the mole fraction and total pressure. * partial pressure is equal to the product of the mole fraction and total pressure.

Answer 386

partial pressure of a component over a solution is proportional to its mole fraction in the liquid.

Question 387

Ammonia present in the coke oven gas is removed by washing with * caustic solution * dilute ammoniacal liquor * dilute HCl * ethanolamine

Answer 387

dilute ammoniacal liquor

Question 388

Which of the following processes is not an example of adsorption applied to gaseous separations ? * Recovery of valuable solvent vapors from dilute mixture with air and other gases. * Dehumidification of air and gas. * Removal of objectionable odour and impurities from industrial gases. * Decolouration of yellow glycerene.

Answer 388

Decolouration of yellow glycerene.

Question 389

The critical moisture content in case of drying indicates the __________ rate period. * beginning of falling * beginning of constant * end of falling * none of these

Answer 389

beginning of falling

Question 390

Pick out the wrong statement * A horizontal line on the humidity chart indicates the temperature changes at constant molal humidity. * When water is cooled from 80 to 70°C by exposure to the air with a wet bulb temperature of 60°C, then both the approach & the range would be 10°C. * For unsaturated air-water vapor mixture at atmospheric conditions, the wet bulb temperature & adiabatic cooling lines are the same. * Relative saturation of unsaturated mixture of water vapor & air can not be increased by either reducing the mixture temperature or by increasing the total pressure.

Answer 390

Relative saturation of unsaturated mixture of water vapor & air can not be increased by either reducing the mixture temperature or by increasing the total pressure.

Question 391

According to Poiseuille's law, the permeability for gas flow through a capillary is proportional to (where, μ = gas viscosity) * μ * 1/μ * μ^1/2 * μ^2

Answer 391

1/μ

Question 392

For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be * 1 * 0 * 2 * 3

Answer 392

1

Question 393

H2S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H2S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y = 5x + 0.001 is * 2.0 * 1.56 * 1.0 * 0.56

Answer 393

2.0

Question 394

For the flow of gases through a capillary, with increase in temperature, the permeability __________ as per Knudsen law. * increases * decreases * remains same * either (a) or (b); depends on the gas

Answer 394

increases

Question 395

Which of the following is directly concerned with psychrometry ? * Lewis relationship * Galileo number * Weber number * Dean number

Answer 395

Lewis relationship

Question 396

Plate efficiency in a distillation column is reduced due to the __________ of liquid. * entrainment * foaming * weeping & dumping * all (a), (b) & (c)

Answer 396

all (a), (b) & (c)

Question 397

The most efficient cooling tower out of the following is * induced draft * forced draft * natural draft * atmospheric

Answer 397

induced draft

Question 398

Sodium bicarbonate is produced during soda ash manufacture using a __________ tower. * plate * baffle * packed * none of these

Answer 398

baffle

Question 399

Powdery materials can be guarded against caking tendency on storage by * providing irregular grain size. * providing minimum percentage of voids. * having maximum possible points of contact. * none of these.

Answer 399

none of these.

Question 400

In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number. * Lewis * Grashoff * Sherwood * none of these

Answer 400

Lewis

Question 401

Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes ? * Packed towers * Plate towers * Spray towers * Wetted wall columns

Answer 401

Wetted wall columns

Question 402

The temperature of water cooled in cooling tower is always __________ temperature of entering air. * more than the wet bulb * less than the wet bulb * equal to the wet bulb * equal to the dry bulb

Answer 402

more than the wet bulb

Question 403

Which of the following processes is followed by unsaturated air (with dry bulb temperature 12°C and relative humidity 47%) passing through water spray washer (temperature of water being constant at 40°C? * Humidification only * Heating only * Both heating and humidification * Evaporative cooling

Answer 403

Both heating and humidification

Question 404

Mass transfer co-efficient is directly proportional to DAB according to the __________ theory. * film * penetration * surface-renewal * none of these

Answer 404

film

Question 405

The relative volatility of a binary mixture at constant temperature __________ the total pressure. * decreases with increase in * increases with increase in * is independent of * none of these

Answer 405

decreases with increase in

Question 406

Tower diameter may be decreased by * using higher reflux ratio. * use of increased tray spacing. * increasing the liquid flow rate. * increasing the vapour flow rate.

Answer 406

use of increased tray spacing.

Question 407

Rayleigh's equation applies to __________ distillation. * continuous * steam * differential * flash

Answer 407

differential

Question 408

Steady state equimolal counter diffusion is encountered in * separation of a binary mixture by distillation. * absorption of NH3 from air by water. * all liquid-liquid diffusion systems. * all liquid-solid diffusion systems.

Answer 408

separation of a binary mixture by distillation.

Question 409

Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation ? * Cost * Availability * Toxicity * Selectivity

Answer 409

Selectivity

Question 410

As the reflux ratio increases, the slope of the operating line for rectifying section * increases * decreases * remains constant * data insufficient, cannot be predicted

Answer 410

increases

Question 411

Cox chart, which is useful in the design of distillation column particularly for petroleum hydrocarbons, is a plot of (where, P = vapor pressure, T = temperature) * log P vs . T * log P vs. log T * T vs. P * P vs . log T

Answer 411

log P vs . T

Question 412

The unit of volumetric diffusivity is * cm^2/sec * cm/sec * cm^3/sec * cm^2/sec^2

Answer 412

cm^2/sec

Question 413

For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates. * binary mixture is represented by the apex * binary mixture is represented by any point inside * ternery mixture is represented by the sides * pure component is represented by the apex.

Answer 413

pure component is represented by the apex.

Question 414

Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the __________ temperature. * dry-bulb * wet-bulb * dew point * adiabatic saturation

Answer 414

wet-bulb

Question 415

The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc) for the same sytem is * 100 * 10 * 5 * 1

Answer 415

10

Question 416

The slope of q-line is determined by the * reflux ratio * plate efficiency to be achieved * thermal condition of the feed * relative volatility.

Answer 416

thermal condition of the feed

Question 417

In steam distillation, the * temperature is 100°C. * temperature is more than 100° C. * product must be immiscible with water. * temperature is higher than the boiling point of either component.

Answer 417

product must be immiscible with water.

Question 418

Which of the following can be calculated theoretically using steam table and Dalton's law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known ? * Dew point * Humidity ratio * Wet bulb temperature * None of these

Answer 418

Wet bulb temperature

Question 419

The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will * increase * decrease * remains same * depend on saturated boiling point; may increase or decrease

Answer 419

increase

Question 420

Rose oil is extracted from rose leaves using __________ distillation. * high pressure * low pressure * extractive * steam

Answer 420

steam

Question 421

Hypersorption refers to a __________ process. * fixed bed absorption * moving bed absorption * fixed bed adsorption * moving bed adsorption

Answer 421

moving bed adsorption

Question 422

Which of the following is the correct ternery diagram for liquid-liquid extraction system comprising of two pairs partly soluble (e.g., chlorobenzene-water-methyl ethyl ketone system) ?

Answer 422

Question 423

Extraction of coffee from its seed is done by * liquid-liquid extraction. * leaching. * extractive distillation. * steam distillation.

Answer 423

leaching.

Question 424

In azeotropic mixture, the equilibrium vapour composition is * more than liquid composition. * less than liquid composition. * same as liquid composition. * independent of pressure.

Answer 424

same as liquid composition.

Question 425

With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux * increases * decreases * remains same * may increase or decrease ; depends on system.

Answer 425

decreases

Question 426

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of * mass diffusivity to momentum diffusivity. * thermal diffusivity to mass diffusivity. * momentum diffusivity to thermal diffusivity. * none of these.

Answer 426

thermal diffusivity to mass diffusivity.

Question 427

According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity) * D * D^2 * D^0.5 * 1/D

Answer 427

D

Question 428

Dry bulb temperature of the gas is __________ the wet bulb temperature. * less than * more than * equal to * none of these

Answer 428

more than

Question 429

Decoction refers to the use of solvent * at ambient temperature * at its boiling point * in its vapor form * none of these

Answer 429

at its boiling point

Question 430

Flash distillation is suitable for separating the constituents of a binary system, which * form minimum boiling azeotrope. * have very wide boiling points. * have very close boiling points. * form constant boiling azeotrope.

Answer 430

have very wide boiling points.

Question 431

The ratio of Murphree plate efficiency to point efficiency is 1 in a __________ flow model. * plug * perfectly mixed * both (a) & (b) * neither (a) nor (b)

Answer 431

perfectly mixed

Question 432

The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm^2/sec. * 0.25 * 2.5 * 1.25 * 0.0025

Answer 432

0.25

Question 433

Flooding in a column results due to * high pressure drop * low pressure drop * low velocity of the liquid * high temperature

Answer 433

high pressure drop

Question 434

Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty ? * Grid tray tower * Perforated tray tower * Wetted wall tower * Bubble cap tower

Answer 434

Wetted wall tower

Question 435

A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture? - The mixture exhibits an azeotrope at 101.3 kPa. - The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10. - The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10. - The mixture contain optical isomers.

Answer 435

The mixture exhibits an azeotrope at 101.3 kPa.

Question 436

Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled * and humidified. * and dehumidified with increase in wet bulb temperature. * at the same relative humidity. * and dehumidified with decrease in wet bulb temperature.

Answer 436

and dehumidified with decrease in wet bulb temperature.

Question 437

The process employing desorption of the absorbed solute by a solvent is called * elution * osmosis * reverse osmosis * sublimation

Answer 437

elution

Question 438

Which of the following operations does not involve leaching ? * Dissolving gold from ores. * Dissolving pharmaceutical products from bark or roots. * Dissolving sugar from the cells of the beet. * Removing nicotine from its water solution by kerosene.

Answer 438

Removing nicotine from its water solution by kerosene.

Question 439

The recovery of pencillin from the acidified fermentation broth is done by * distillation * evaporation * absorption * liquid extraction

Answer 439

liquid extraction

Question 440

Molecular seives are porous * alumina. * silica. * synthetic zeolites crystals/metal alumino-silicates. * none of these.

Answer 440

synthetic zeolites crystals/metal alumino-silicates.

Question 441

Calcium ammonium nitrate (a fertiliser) is dried in a __________ dryer. * rotary * vacuum * tunnel * tray

Answer 441

rotary

Question 442

A binary mixture of benzene and cyclohexane is separated by * flash vaporisation * extractive distillation * solvent extraction * ordinary distillation

Answer 442

extractive distillation

Question 443

Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular difusion, if * mass transfer is accompanied by reaction. * diffusion of A is in stagnant medium B. * molecular mean free path is high. * there is equimolar counter diffusion.

Answer 443

there is equimolar counter diffusion.

Question 444

Cox chart is useful in the design of * distillation column * evaporator * dryer * crystalliser

Answer 444

distillation column

Question 445

Dew point of an air-water vapor mixture * decreases with decrease in pressure. * at constant humidity & total pressure is fixed. * corresponding to any point on the humidity chart is obtained by projecting a line through this point parallel to the temperature axis and to the saturation curve. * all 'a', 'b' & 'c'.

Answer 445

all 'a', 'b' & 'c'.

Question 446

Can a cooling tower cool water below the wet bulb temperature of inlet air ? * yes * no * yes ; but height of cooling tower will be prohibitively high. * yes ; but the air flow rate should be excessively high.

Answer 446

no

Question 447

The suitable evaporator for concentration of foaming liquids is a __________ evaporator. * long tube * short tube * vacuum * falling film

Answer 447

long tube

Question 448

The ratio of Murphree plate efficiency to point efficiency is always > 1 in a __________ flow model. * plug * perfectly mixed * both (a) & (b) * neither (a) nor (b)

Answer 448

plug

Question 449

Tea percolation employs * liquid-liquid extraction * leaching * absorption * none of these

Answer 449

leaching

Question 450

Which of the following assumes constant molal vaporisation and overflow ? * McCabe-Thiele method * Ponchan-Savarit method * Enthalpy concentration method * Plate absorption column

Answer 450

McCabe-Thiele method

Question 451

Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be * 1 * > 1 * < 1 * ≤ 1

Answer 451

> 1

Question 452

Selectivity of the solvent used in solvent extraction should be * 1 * > 1 * < 1 * 0

Answer 452

> 1

Question 453

Pick out the wrong statement pertaining to leaching. * Fine solids can not be leached in a Pachuka tank. * Door classifier can be used for leaching of coarse solids. * Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor. * Very high temperature is not needed for the leaching of sugar beet.

Answer 453

Fine solids can not be leached in a Pachuka tank.

Question 454

Wet bulb and dry bulb temperatures becomes identical at __________ percent saturation curve. * 100 * 50 * 78 * none of these

Answer 454

100

Question 455

NSc/NPr is called the * psychrometric ratio * Lewis number * Sherwood number * Stantan number

Answer 455

Lewis number

Question 456

McCabe-Thiele method * uses molal units for material and energy balance. * uses weight fractions to express liquid and vapour composition. * can use any type of units. * is more accurate than Ponchan-Savarit method.

Answer 456

uses molal units for material and energy balance.

Question 457

The film penetration model of mass transfer was enunciated by * Gilliland * Toor and Marchello * Stefan * Fick

Answer 457

Toor and Marchello

Question 458

The most economical range of absorption factor is * 0 to 0.5 * 0 to 3 * 1.25 to 2 * 5 to 15

Answer 458

1.25 to 2

Question 459

Channelling is most severe * in towers packed with stacked packing. * in towers packed randomly with crushed solids. * in dumped packing of regular units. * at very high liquid flow rate.

Answer 459

in towers packed with stacked packing.

Question 460

Out of two equilibrium curves, first one lies above the diagonal and the second lies below the diagonal in the x-y plot. It means that separation by distillation is * not possible in the second case unless vacuum is applied. * not possible in the second case unless high pressure is applied. * more readily done in the second case compared to first one. * none of these

Answer 460

more readily done in the second case compared to first one.

Question 461

'ADDUCTS' and 'CLATHRATES' are used in case of * extractive distillation. * crystallisation. * absorption. * none of these.

Answer 461

crystallisation.

Question 462

Adsorption is an unit operation which generally involves __________ systems. * liquid-solid * gas-solid * fluid-solid * solid-solid

Answer 462

fluid-solid

Question 463

In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated. * molecular * azeotropic * extractive * flash.

Answer 463

extractive

Question 464

Separation of the isotopes of helium for scientific investigations is done by * reverse osmosis * thermal diffusion * leaching * solvent extraction

Answer 464

thermal diffusion

Question 465

In a binary system, separation is very efficient, when the relative volatility is * 1 * > 1 * < 1 * 0.5

Answer 465

> 1

Question 466

Fenske-Underwood equation used for calculating the minimum number of theoretical plates in distillation column is valid for * constant molal overflow * total reflux * constant relative volatility * all (a), (b) and (c)

Answer 466

all (a), (b) and (c)

Question 467

The binary diffusivity in gases does not depend upon the * pressure * temperature * nature of the components * none of these

Answer 467

none of these

Question 468

Berl saddle made of carbon cannot be used for * alkalis * SO2 * H2SO4 * oxidising atmosphere

Answer 468

oxidising atmosphere

Question 469

1 kg of a saturated aqueous solution of a highly soluble component A at 60°C is cooled to 25°C. The solubility limits of A are (0.6 kgA/kg water) at 60°C and (0.2 kgA/kg water) at 25°C. The amount in kg of the crystals formed is * 0.4 * 0.25 * 0.2 * 0.175

Answer 469

0.2

Question 470

Priming in a distillation column * results from very low gas velocity. * is desirable from point efficiency consideration. * is characterised by the presence of foam throughout the space between trays. * reduces the overall pressure drop.

Answer 470

is characterised by the presence of foam throughout the space between trays.

Question 471

The commonly used solvent in supercritical extraction is * methyl ethyl ketone. * water. * carbon tetrachloride. * carbon dioxide.

Answer 471

carbon dioxide.

Question 472

When the liquid over a plate is of uniform concentration, then * Murphree efficiency > point efficiency. * Murphree efficiency < point efficiency. * Murphree efficiency = point efficiency. * Murphree efficiency ≠ point efficiency.

Answer 472

Murphree efficiency = point efficiency.

Question 473

In saturated gas, the * vapour is in equilibrium with the liquid at the gas temperature. * vapour is in equilibrium with the liquid at the room temperature. * partial pressure of vapour equals the vapour pressure of the liquid at room temperature. * none of these.

Answer 473

vapour is in equilibrium with the liquid at the gas temperature.

Question 474

As per Gilliland's equation, the diffusivity is * directly proportional to 'T^1.5'. * inversely proportional to 'P'. * dependent on the molecular volume & molecular weight of components. * all 'a', 'b' & 'c'.

Answer 474

all 'a', 'b' & 'c'.

Question 475

Pick out the wrong statement. * When the concentration difference for the mass transfer becomes zero at the bottom of the gas absorption tower, then the upper end of the operating line touches the equilibrium curve. * The average distance between the operating line and equilibrium line is large, when the liquid-gas ratio is also large in case of a counter current gas absorption tower. * The operating line lies above the equilibrium curve in case of a gas desorber. * With decrease in the liquid flow rate for a fixed gas flow rate, the slope of the operating line decreases, in case of gas absorption process.

Answer 475

The operating line lies above the equilibrium curve in case of a gas desorber. true ans: The average distance between the operating line and equilibrium line is large, when the liquid-gas ratio is also large in case of a counter current gas absorption tower.

Question 476

A mixture of 10% C6H6 vapour in air at 25°C and 750 mm Hg has a dew point of 20°C. Its dew point at 30°C and 700 mm Hg will be around __________ °C. * 21.7 * 20 * 27.3 * 18.7

Answer 476

18.7

Question 477

Which of the following is not fixed by the process requirements, in the design of absorbers ? * Flow rate of the entering gas. * Composition of the entering liquid. * Terminal concentrations of gas stream. * None of these.

Answer 477

None of these.

Question 478

If the amount of the steam used in steam distillation is increased, the temperature of distillation * increases * decreases * remains unchanged * depends on relative volatility

Answer 478

decreases

Question 479

moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture. * unbound * critical * free * bound

Answer 479

unbound

Question 480

Inside the distillation columns, the * highest temperatures is near the feed plate. * driving force for the liquid flow is its weight. * vapors are not always at their dew points. * all (a), (b) and (c)

Answer 480

driving force for the liquid flow is its weight.

Question 481

When the psychometric ratio is __________ then the adiabatic saturation temperature and wet bulb temperature becomes equal. * 1 * < 1 * > 1 * ∞

Answer 481

1

Question 482

Desirable value of absorption factor in an absorber is * 1 * < 1 * > 1 * 0.5

Answer 482

> 1

Question 483

Refractory bricks are usually dried in a __________ dryer. * tray * tunnel * conveyor * festoon

Answer 483

tunnel

Question 484

What is the degree of freedom of an absorption process in which only one component is transferred between phases ? * 3 * 2 * 4 * 1

Answer 484

3

Question 485

Sticky material can be dried in a __________ dryer. * tray * rotary * fluidised bed * none of these

Answer 485

tray

Question 486

Langmuir equation is associated with * leaching * adsorption * steam distillation * multicomponent absorption.

Answer 486

adsorption

Question 487

During the constant rate period of drying of a solid, * increased air humidity decreases the rate of drying. * increasing the air temperature decreases the drying rate. * surface evaporation of unbound moisture occurs. * none of these.

Answer 487

surface evaporation of unbound moisture occurs.

Question 488

At a fixed total pressure, humidity depends only on the * partial pressure of vapour in the mixture. * heat capacity of the vapour. * density of the vapour. * none of these.

Answer 488

partial pressure of vapour in the mixture.

Question 489

If moisture content of solid on dry basis is X, then the same on wet basis is * x/(x+1) * x/(1-x) * (1+x)/x * (1-x)/x

Answer 489

x/(x+1)

Question 490

Flash distillation is * same as differential distillation. * used for multicomponent systems like crude refining. * same as simple distillation. * most useful for handling binary systems.

Answer 490

used for multicomponent systems like crude refining.

Question 491

__________ developed the film theory. * Higbie * Fick * Ergun * Levenspeil

Answer 491

Higbie

Question 492

For absorbers, high pressure drop results in * increased efficiency. * decreased efficiency. * high operating cost. * better gas liquid contact.

Answer 492

high operating cost.

Question 493

Which of the following parameters remains almost constant during adiabatic saturation of unsaturated air ? * Dry bulb temperature * Dew point * Wet bulb temperature * None of these

Answer 493

Wet bulb temperature

Question 494

Coffee is prepared from coffee beans by leaching with * cold water * hot water * dilute hot caustic solution * naphtha

Answer 494

hot water

Question 495

Gaseous diffusion co-efficient increases with increase in the * pressure * temperature * both (a) & (b) * neither (a) nor (b)

Answer 495

temperature

Question 496

With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature) * increases * remains unchanged * decreases * decreases linearly

Answer 496

increases

Question 497

If xD = overhead product molal composition and RD = reflux ratio, then slope and intercept of the operating line for rectifying section are respectively * xD/ (RD+1) , RD/ (RD+1) * RD/ (RD+1) , xD/ (XD+1) * xD/ (RD+1) , (RD+1)/ RD

Answer 497

RD/ (RD+1) , xD/ (XD+1)

Question 498

Pick out the wrong statement. Raoult's law does not apply, when the * size of component molecules are not equal. * attractive forces between like and unlike molecules in the solution are approximately equal. * component molecules are nonpolar. * chemical combination or molecular association between unlike molecules takes place in the formation of solution.

Answer 498

component molecules are nonpolar. true ans: attractive forces between like and unlike molecules in the solution are approximately equal.

Question 499

Water-ethyl alcohal solution can be concentrated (in respect of alcohal concentration) by __________ distillation. * atmospheric * vacuum * high pressure * none of these

Answer 499

vacuum

Question 500

L/mGis the expression for * absorption factor * Brinkman number * slope of operating line in absorber * slope of operating line in stripper.

Answer 500

absorption factor

Question 501

Extraction of pencillin employs a __________ extraction coloumn. * centrifugal * packed * plate * None of these.

Answer 501

centrifugal

Question 502

In case of gases, the binary diffusivity is proportional to (where, P = pressure) * P * 1/P * 1/(P)^1/2 * (P)^1/2

Answer 502

1/P

Question 503

When the gas to be dissolved in liquid is a/an __________ then normally co-current adsorber are used. * mixture of two gases * pure gas * ideal gas * sparingly soluble gas

Answer 503

pure gas

Question 504

Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the __________ number. * Schmidt * Sherwood * Peclet * Stanton

Answer 504

Schmidt

Question 505

If a two phase system is in physical equilibrium; then it means that, the * escaping tendency of each component from the liquid phase to the vapor phase is exactly equal to that from vapor phase to liquid phase. * temperature of the liquid phase is equal to that of the vapor phase. * total pressure throughout the liquid phase is equal to that throughout the vapor phase. * all (a), (b) and (c).

Answer 505

all (a), (b) and (c).

Question 506

McCabe-Thiele method of binary distillation does not assume that the * sensible heat changes are negligible compared with latent heat changes. * molar latent heats of all components are equal. * heat of mixing is negligible. * none of these

Answer 506

none of these

Question 507

(NSh/NRe.NSc) is termed in mass transfer operation as the * Stanton number * Peclet number * thermal diffusivity * momentum diffusivity

Answer 507

Stanton number

Question 508

The Hatta number is important in * multicomponent distillation. * binary distillation. * gas absorption without chemical reaction. * gas absorption with chemical reaction.

Answer 508

gas absorption with chemical reaction.

Question 509

When a multistage tray tower uses a minimum reflux ratio, it implies * infinite trays and maximum reboiler heat load. * infinite trays and minimum reboiler heat load. * minimum trays and minimum reboiler heat load. * minimum trays and maximum reboiler heat load

Answer 509

infinite trays and minimum reboiler heat load.

Question 510

CO2 can be absorbed by * hot cupric oxide * heated charcoal * cold Ca(OH)2 * alumina

Answer 510

heated charcoal

Question 511

For the same process conditions, the reflux ratio of an unlagged distillation column * decreases in winter * increases in winter * increases in summer * none of these

Answer 511

increases in winter

Question 512

An ideal tower packing should not * have low weight per unit volume. * have large surface area per unit volume. * have large free cross-section. * hold up large amount of liquid in the packing.

Answer 512

hold up large amount of liquid in the packing.

Question 513

Which of the following is a suitable absorbent for removal of H2S from natural gas ? * Vetrocoke solution * Monoethanol amine (MEA) * Dilute * Hot water

Answer 513

Monoethanol amine (MEA)

Question 514

Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (yin = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is, N+2 = 6 log (yin/yout).For 98% recovery of acetone, the number of trays required is/are * 1 * 8 * 9 * 10

Answer 514

9

Question 515

Schimdt number and Lewis number for pure air at atmospheric conditions are respectively * < 1 and ≈ 1 * 1 and 0 * >1 and ≈ 1 * 0 and ≈ 1

Answer 515

< 1 and ≈ 1

Question 516

Below is given an equilibrium moisture curve of a substance. State which regions represent free moisture and unbound moisture respectively. (insert graph here S12P1) * II, III * II, IV * IV, III * IV, II

Answer 516

II, III

Question 517

Molecular diffusion is caused by the * transfer of molecules from low concentration to high concentration region. * thermal energy of the molecules. * activation energy of the molecules. * potential energy of the molecules.

Answer 517

thermal energy of the molecules.

Question 518

At __________ reflux, theoretical number of plates in a distillation coloumn is calculated using Fenske-Underwood equation. * operating * total * minimum * maximum permissible

Answer 518

total

Question 519

Separation of a mixture of two gases by absorption in the liquid solvent depends upon the difference in their * viscosity * density * solubility * relative volatility

Answer 519

solubility

Question 520

Components, having widely different boiling point in a binary mixture, can be separated using __________ distillation. * molecular * extractive * steam * simple

Answer 520

simple

Question 521

Which of the following equipments is not used in liquid-liquid extraction ? * Pachuka tank * Agitated vessels * Centrifugal extractors * Packed towers

Answer 521

Pachuka tank

Question 522

Pick out the wrong statement. * Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the possibility of tower wall collapse. * Packed towers are preferred over plate towers for handling corrosive and foamy liquids. * Diameter of randomly packed tower is normally more than 1.2 metres. * Due to uneven supply and improper distribution of liquid, problem of channeling, loading & flooding is generally encountered in packed towers.

Answer 522

Diameter of randomly packed tower is normally more than 1.2 metres.

Question 523

Equilibrium-moisture curves of different solids * are different * are same * depend on the humidity of the gas * none of these

Answer 523

are differenT

Question 524

Azeotropism for ethyl alcohol-water system disappears by * increasing temperature * decreasing pressure * increasing pressure * no means

Answer 524

decreasing pressure

Question 525

Degree of freedom for leaching and solvent extraction process is * 1 * 3 * 0 * 2

Answer 525

3

Question 526

Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the * mass transfer co-efficient. * thermal diffusivity. * kinematic viscosity. * volumetric diffusivity.

Answer 526

mass transfer co-efficient.

Question 527

Equilibrium moisture of a solid is equal to the total moisture minus free moisture. Which of the following substances will have maxi-mum equilibrium moisture ? * Anthracite coal * Rag paper * Bamboo * Inorganic solids

Answer 527

Bamboo

Question 528

Drying of refractory is normally carried out in a __________ dryer. * open pan * tray * rotary vacuum * truck/tunnel.

Answer 528

truck/tunnel.

Question 529

The expression, ln(F/W) = ∫dx/(y*-x) from xW to xF is * differential distillation equation * for NtoG in absorption for dilute mixture * slope of q-line in McCabe-Thiele method * for relative volatility

Answer 529

differential distillation equation

Question 530

Heat sensitive materials with very high latent heat of vaporisation may be economically separated using * liquid extraction * distillation * evaporation * absorption

Answer 530

liquid extraction

Question 531

When the solvent dissolves very little of solute, then * solvent of low latent heat of vaporisation should be used. * solvent of low freezing point should be used. * large quantity of solvent is required to extract the solute. * very small quantity of solvent is required.

Answer 531

large quantity of solvent is required to extract the solute.

Question 532

An alkaline solution is used to reduce the concentration of carbon dioxide in a stream from 10% to 0.1% by absorption with irreversible chemical reaction. The overall number of transfer units based on gas phase is * 9.21 * 4.605 * 100 * 0.001

Answer 532

4.605

Question 533

HETP is numerically equal to HTU, only when the operating line * lies below the equilibrium line. * lies above the equilibrium line. * and equilibrium lines are parallel. * is far from the equilibrium line.

Answer 533

and equilibrium lines are parallel.

Question 534

In a distillation operation, what is the effect of the temperature of the reflux stream (given below) on the condenser and reboiler loads ? Reflux conditions: (i) Reflux stream is completely liquid and is at its bubble point. (ii) Reflux stream is below its bubble point. * Condenser and reboiler loads are the same in both the cases. * Reboiler load is the same in both the cases but condenser load is higher in case (ii). * Condenser load is the same in both the cases but reboiler load is higher in case (ii). * Both condensor and reboiler loads are higher in case (ii) as compared to case (i).

Answer 534

Both condensor and reboiler loads are higher in case (ii) as compared to case (i).

Question 535

Steady state equimolal counter diffusion occurs in case of * leaching * absorption * binary phase distillation * liquid-liquid extraction

Answer 535

binary phase distillation

Question 536

JD factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by * Nsh = 2 * Nst = 2 * Nsc = 2 * none of these

Answer 536

Nsh = 2

Question 537

The relative saturation of an unsaturated mixture of gas and vapor is independent of the * nature of the vapor. * temperature of the mixture. * composition of the mixture. * none of these.

Answer 537

none of these.

Question 538

The adiabatic saturation curve for a vapour-gas mixture is * straight line. * slightly concave upward. * slightly concave downward. * none of these.

Answer 538

slightly concave upward.

Question 539

Pick out the wrong statement. * Cellulose acetate membranes are used in dialysis process. * Elutriation process refers to when the soluble material is largely concentrated on the surface of an insoluble solid and is simply washed off by the solvent. * 'Cascade' means a group of stages interconnected so that various streams flow from one to another. * Zirconia probe is used for the humidity measurement.

Answer 539

Zirconia probe is used for the humidity measurement.

Question 540

The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases 'A' and 'B' is * 1 * ∞ * 0.5 * 2

Answer 540

∞

Question 541

Drift in a cooling tower is * the water entrained by the circulating air. * dependent on the water lost by evaporation. * desirable. * all (a), (b) & (c).

Answer 541

the water entrained by the circulating air.

Question 542

With increase in the concentration of the adsorbate, the integral heat of adsorption * increases. * decreases. * remains unchanged. * may increase or decrease ; depends on the type of adsorbate.

Answer 542

decreases.

Question 543

Small dia distillation column can be a * packed column * sieve tray * bubble cap * any of these

Answer 543

packed column

Question 544

If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is * 0 * 1 * < 1 * > 1

Answer 544

1

Question 545

An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is * 0.048 * 0.079 * 0.122 * 0.152

Answer 545

0.152

Question 546

__________ column is used in gas absorption process. * Wetted wall * Seive/perforated tray * Bubble cap * Packed

Answer 546

Packed

Question 547

Nitrobenzene (boiling point = 210.6°C) is steam distilled at 1 atm pressure.Nitrobenzene will distill off __________ °C. * at < 100 * at > 210.6 * between 100 and 210 * none of these

Answer 547

at < 100

Question 548

Pick out the wrong statement. * With decrease in feed temperature, the number of plates required for binary distillation decreases for a given L/V ratio. * The extraction per unit of total height for a short packed column is more effective than for a tall column, in case of liquid-liquid extraction. * Natural draft cooling towers are made of ferro-concrete and its cross-section is wider at the bottom. * Vanderwall adsorption is also called chemisorption.

Answer 548

Vanderwall adsorption is also called chemisorption.

Question 549

At what value of reflux ratio, number of theoretical plates in a distillation column is minimum ? * 0 * 1 * ∞ * < 1

Answer 549

∞

Question 550

Batch tray dryers suffers from the disadvantage of * high maintenance cost. * non-uniform & low production rate. * high labour cost & low heat economy. * all 'a', 'b' & 'c'.

Answer 550

high labour cost & low heat economy.

Question 551

In a moderately sized packed absorption tower, channeling (which is most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter * >4:1 * <8:1 * > 8:1 * <6:1

Answer 551

> 8:1

Question 552

__________ column is preferred to be used, when a high liquid hold up is required in a reactor for gas-liquid reaction. * Packed * Bubble * Spray * Tray

Answer 552

Bubble

Question 553

Penetration model (theory) for mass transfer was enunciated by * Danckwerts * Toor and Marchello * Higbie * Kissinevskii

Answer 553

Higbie

Question 554

Surface renewal model of mass transfer was enunciated by * Toor and Marchello * Fick * Danckwerts * Stefan

Answer 554

Danckwerts

Question 555

When the __________ the relative humidity of air decreases, despite an increase in the absolute humidity. * temperature rises * pressure rises * temperature falls * pressure falls

Answer 555

temperature rises

Question 556

For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as * Re^0.33 * Re^0.53 * Re^0.83 * Re

Answer 556

Re^0.83

Question 557

The relative humidity of air decreases in-spite of an increase in the absolute humidity, when the * temperature rises. * pressure rises. * temperature falls. * pressure falls.

Answer 557

temperature rises.

Question 558

Unit of molal diffusivity is * cm^2/sec gm . mole * gm moles/cm^2 . sec * gm moles/cm. sec * gm moles/cm^2. sec

Answer 558

gm moles/cm. sec

Question 559

The term "approach" in a cooling tower refers to the difference in the temperature of the * cold water leaving the tower and the wet bulb temperature of the surrounding air. * hot water entering the tower and the wet bulb temperature of the surrounding air. * hot water entering and the cooled water leaving the cooling tower. * none of these

Answer 559

cold water leaving the tower and the wet bulb temperature of the surrounding air.

Question 560

Binary distillation involves the mass transfer by __________ at the gas-liquid interface. * unidirectional diffusion from liquid to gas phase * unidirectional diffusion from gas to liquid phase * either 'a' or 'b' * a counter diffusion at an almost equal molar rate

Answer 560

a counter diffusion at an almost equal molar rate

Question 561

In a gas-liquid absorption coloumn, for obtaining the maximum absorption efficiency * liquid stream should be distributed uniformly. * gas stream should be distributed uniformly. * both gas as well as liquid streams should be distributed uniformly. * by passing should be completely avoided.

Answer 561

both gas as well as liquid streams should be distributed uniformly.

Question 562

Reverse osmosis is also called * dialysis * electrodilysis * diffusion * ultrafiltration.

Answer 562

ultrafiltration.

Question 563

Which of the following is not a batch drier? * Truck drier * Agitated pan drier * Fluidised bed drier * Vacuum shelf drier

Answer 563

Fluidised bed drier

Question 564

Steam distillation is not recommended to be used, if the * azeotropic mixture is to be separated and the final product is miscible with water. * liquids decompose, if distilled directly at atmospheric pressure. * material can not be distilled by indirect heating even under low pressure, because of the high boiling temperature. * material to be distilled is thermally unstable or has the tendency to react with other components associated with it, at the boiling temperature.

Answer 564

azeotropic mixture is to be separated and the final product is miscible with water.

Question 565

Rayleigh equation applies to __________ distillation. * differential * flash * equilibrium * molecular

Answer 565

differential

Question 566

Mass transfer co-efficient 'K' according to penetration theory varies with mass dif-fusivity as * D^0.5 * D * 1/D * D^1.5

Answer 566

D^0.5

Question 567

Most important factor to be considered in the selection of packings for absorbers is the __________ of packing. * size * durability * porosity * cost

Answer 567

porosity

Question 568

__________ is the separation technique used for desalination of sea water. * Thermal diffusion * Reverse osmosis * Adsorption * absorption

Answer 568

Reverse osmosis

Question 569

Danckwerts developed the __________ theory. * penetration * surface renewal * film * none of these

Answer 569

surface renewal

Question 570

Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant humidity velocity temperature all (a), (b) & (c)

Answer 570

all (a), (b) & (c)

Question 571

Which of the following provides maximum contact surface for a liquid-vapour system? * Packed tower * Bubble-cap plate column * Seive-plate column * Wetted wall column

Answer 571

Packed tower

Question 572

For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is * calculated * unknown * known * not required

Answer 572

known

Question 573

In stripping section of continuous distillation column, the * liquid is stripped of high boiler. * liquid is enriched with high boiler. * vapour is stripped of low boiler. * none of these.

Answer 573

liquid is enriched with high boiler.

Question 574

Molality is defined as the number of gm moles of solute per __________ of solvent. * litre * gm * Kg * m^3

Answer 574

Kg

Question 575

__________ is concerned with the adsorption equilibria. * Fick's law * Gibb's equation * Freundlich equation * none of these

Answer 575

Freundlich equation

Question 576

Which of the following is the correct ternery diagram for liquid-liquid extraction system comprising of one pair partly soluble (e.g. water-benzene-acetic acid in which A-diluent, B - solvent and C - solute)?

Answer 576

Question 577

Fractional solvent extraction * employs only one solvent * employs two solvents * results in low interfacial tension * none of these

Answer 577

employs two solvents

Question 578

In the layout plan for a vacuum distillation unit, operating at 60 mm Hg, supported by a barometric condenser, the appropriate place for the location of vacuum drum for collecting the distillate will be * at ground level. * 2 metres above the ground. * 5 metres above ground. * 10 metres above ground.

Answer 578

at ground level.

Question 579

Raschig ring made of procelain cannot be used for treating concentrated * hydrochloric acid * nitric acid * alkalis * sulphuric acid

Answer 579

alkalis

Question 580

H2S present in naphtha reformed gas is removed by absorbing with * ethanolamine * K2CO3 * HCl * vacuum gas oil

Answer 580

ethanolamine

Question 581

During constant rate drying period, vaporisation rate per unit drying surface area - decreases with time. - increases with time. - does not change with time, - does not affect the moisture content of the wet solid.

Answer 581

does not change with time,

Question 582

Pick out the wrong statement. * Mass transfer co-efficient does not account for gase-liquid diffusion. * Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation. * Contacting cold vapor-gas mixture with hot liquid exemplifies humidification process. * Contacting cold liquid with warm vapor-gas mixture exemplifies dehumidification process.

Answer 582

Mass transfer co-efficient does not account for gase-liquid diffusion.

Question 583

In rectifying section of a continuous distillation column, the * vapour is enriched with low boilers. * vapour is enriched with high boilers. * liquid is stripped of high boilers. * none of these.

Answer 583

vapour is enriched with high boilers.

Question 584

According to Chilton-Colburn analogy for mass transfer, NSt.NSc2/3 is equal to * f * f/2 * 2f * 1/f

Answer 584

f/2

Question 584

For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams * increases * decreases * remains unaffected * passes through a maximum

Answer 584

increases

Question 585

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is * 0.54 * 1.04 * 1.24 * 1.94

Answer 585

1.24

Question 586

Minimum reflux ratio in a distillation column results in * optimum number of trays. * minimum reboiler size. * maximum condenser size. * minimum number of trays.

Answer 586

maximum condenser size.

Question 587

Flooding in a distillation column is detected by a sharp * increase in Murphree plate efficiency. * decrease in pressure drop. * decrease in liquid hold up in the coloumn. * increase in pressure drop.

Answer 587

increase in pressure drop.

Question 588

In extraction, as the temperature increases, the area of hetrogeneity (area covered by binodal curve) * decreases * increases * remains unchanged * none of these

Answer 588

decreases

Question 589

Pick out the wrong statement. * The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr = 1. * 1 Nm^3 of dry air is lighter than 1Nm^3 of humid air. * The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity. * An azeotropic mixture of two liquids has boiling point higher than either of them, when it shows negative deviation from Raoult's Law.

Answer 589

1 Nm^3 of dry air is lighter than 1Nm^3 of humid air.

Question 590

In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation. * lower than * higher than * equal to * either (a) or (b), depends on the mixture composition

Answer 590

lower than

Question 591

At constant pressure, with increase of temperature, the dew point will * increase * decrease * remain unchanged * increase/decrease ; depends on the temperature

Answer 591

increase

Question 592

For a single component absorber, the operating line is straight only when plotted in term of __________ units. * partial pressure * mole ratio * mole fraction * none of these

Answer 592

mole ratio

Question 593

For a binary mixture with low relative volatility, * use steam distillation. * use molecular distillation. * use high pressure distillation. * an azeotrope may be formed during distillation.

Answer 593

an azeotrope may be formed during distillation.

Question 594

Plate efficiency * is a function of the mass transfer between liquid and vapour. * increases due to foaming. * increases due to liquid entrainment. * increases due to weeping and dumping of liquid.

Answer 594

is a function of the mass transfer between liquid and vapour.

Question 595

Absorption accompanied by heat evolution results in * increased capacity of the absorber. * increase in equilibrium solubility. * decrease in equilibrium solubility. * none of these.

Answer 595

decrease in equilibrium solubility.

Question 596

Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the * high evaporation losses of water. * high pressure drop of the gas. * difficulty in its fabrication. * none of these.

Answer 596

high pressure drop of the gas.

Question 597

For a distillation column operating at minimum reflux, the * concentration of liquid and vapour leaving a plate will be same. * reflux ratio will be maximum. * number of plates required will be maximum. * none of these.

Answer 597

number of plates required will be maximum.

Question 598

A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)) * M(Xo - XF) * M(Xo/XF) * M ln(Xo/XF) * MXo ln(Xo/XF)

Answer 598

MXo ln(Xo/XF)

Question 599

Flash distillation is suitable for the separation of components * having very close boiling points. * which form maximum boiling azeotrope. * having very wide boiling points. * which form minimum boiling azeotrope.

Answer 599

having very wide boiling points.

Question 600

In Mcabe-Thiele method, at infinite reflux ratio - number of plates is maximum. - overhead product is maximum. - both the operating lines coincide with the diagram. - none of these.

Answer 600

both the operating lines coincide with the diagram.

Question 601

Leaching rate is independent of the * agitation * temperature * particle size * none of these

Answer 601

none of these

Question 602

Use of packed towers for distillation is generally limited to the * small sizes. * multicomponent distillation. * high pressure operation. * vacuum distillation.

Answer 602

small sizes.

Question 603

Pick out the wrong statement. * The binary diffusivity in liquids is of the order of 10^-5 cm^2 /sec. * Molecular diffusion in solid is much faster than that in liquids. * Particles movement from higher concentration to lower concentration takes place in diffusion process. * According to Poiseuille's law, the permeability decreases with increase in temperature for flow of a gas through a given capillary.

Answer 603

Molecular diffusion in solid is much faster than that in liquids.

Question 604

Which of the following decreases during evaporative cooling process with recirculated water supply ? * Wet bulb temperature * Relative humidity * Partial pressure of vapour * None of these

Answer 604

None of these

Question 605

Laboratory determination of the diffusivity of vapor is done by __________ method. * wetted wall column * Gilliland's * Winkel mann's * Wike's

Answer 605

Winkel mann's

Question 606

The minimum liquid rate to be used in an absorber corresponds to an operating line * of slope = 1 * of slope = 0.1 * tangential to the equilibrium curve * none of these

Answer 606

tangential to the equilibrium curve

Question 607

Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be * cooled * humidified * both (a) & (b) * dehumidified

Answer 607

humidified

Question 608

For absorbing a sparingly soluble gas in a liquid, the * gas side co-efficient should be increased. * liquid side coefficient should be increased. * gas side co-efficient should be decreased. * liquid side co-efficient should be decreased.

Answer 608

liquid side coefficient should be increased.

Question 609

A natural draft cooling tower is filled with wooden grids, which covers about __________ percent of the tower height. * 10-15 * 30-40 * 70-80 * 90-100

Answer 609

10-15

Question 610

The boiling points of pure components of a binary system __________ with increase in total pressure of the system. * decreases * increases * remains unchanged * may increase or decrease, depends on the system.

Answer 610

increases

Question 611

The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the * differential heat of adsorption. * heat of wetting. * integral heat of adsorption. * none of these.

Answer 611

differential heat of adsorption.

Question 612

Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as * K ∝ D * K ∝ D^1/2 * K ∝ D^1.5 * K ∝ D^2

Answer 612

K ∝D^1/2

Question 613

Desulphurisation of petrol is done in a * Bollman extractor * rotating disc extractor * packed extraction column * plate type extraction column

Answer 613

rotating disc extractor

Question 614

Chemisorption compared to physical absorption has * lower adsorption rate. * lower capacity of the solvent for the solute gas. * increased utilization of stagnant zones of the liquid phase. * none of these.

Answer 614

increased utilization of stagnant zones of the liquid phase.

Question 615

Rate of adsorption increases as the * temperature increases. * temperature decreases. * pressure decreases. * size of adsorbent increases.

Answer 615

temperature decreases.

Question 616

Pick out the system with maximum boiling azeotrope at 1 atm. * acetone chloroform * ethyl alcohol-water * benzene-ethyl alcohol * none of these

Answer 616

acetone chloroform

Question 617

At 750°K and 1 atm, the approximate value of Schmidt number for air is * 0.01 * 0.1 * 1 * 10

Answer 617

0.1

Question 618

Calculation of mass transfer co-efficient is mostly/normally done using __________ theory. * surface renewal * film * penetration * none of these.

Answer 618

film

Question 619

The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if * NSc = 1 * NSc = NPr = NLe * NPr = NLe * NSc = NLe

Answer 619

NSc = NPr = NLe

Question 620

For the gas absorption, the height of a transfer unit, based on the gas phase is given by (G: superficial molar gas velocity, L: superficial molar liquid velocity, FG:mass transfer co-efficient, mols/m2 , a: in-terfacial area per unit volume of tower) * G/(FG*a) * FG/(G*a) * (G*a)/FG * L/(FG*G)

Answer 620

G/(FG*a)

Question 621

Which of the following is used for the concentration of rubber latex ? * Agitated film evaporator * Long tube vertical evaporator * Short tube evaporator * Calendria

Answer 621

Agitated film evaporator

Question 622

As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages * increase * decrease * remain unchanged * can either increase or decrease, depends on the system

Answer 622

decrease

Question 623

In triangular co-ordinates, the ternery composition point falls __________ of the triangle. * in the corners * inside * on the sides * none of these.

Answer 623

inside

Question 624

In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raf-finate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg) * 6.89 * 8.89 * 10 * 8.25

Answer 624

8.89

Question 625

Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time) * (De.t)^1/2 * (De/t)^1/2 * (4De/πt)^1/2 * (4De/t)

Answer 625

(4De/πt)^1/2

Question 626

Reboiler is considered as one theoretical plate, because * of the assumption that vapour and liquid leaving the reboiler are in equilibrium. * vapour is recycled to the column. * reboiler itself contains one plate. * none of these.

Answer 626

of the assumption that vapour and liquid leaving the reboiler are in equilibrium.