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Philippine Chemical Engineering Licensure Examination Day 2 Separation Processes > IndiaBIX Chemical Engineering: Mass Transfer Section 2 > Flashcards

IndiaBIX Chemical Engineering: Mass Transfer Section 2 Flashcards

1
Q
  1. The McCabe Δ L law states that the
    A. molar heats of vaporisation of components are nearly equal.
    B. linear crystal growth rate depends on the degree of supersaturation.
    C. linear crystal growth rate does not depend on the crystal size.
    D. linear crystal growth rate depends on the crystal size.
A

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

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2
Q
  1. Bollman extractor
    A. is a static bed leaching equipment.
    B. is used for extraction of oil from oilseed.
    C. is a centrifugal extractor.
    D. employs only counter-current extraction.
A

is used for extraction of oil from oilseed.

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3
Q
  1. The relation, Sc = Pr = 1, is valid, when the mechanism of __________ ansfer is same.
    A. heat and mass
    B. mass and momentum
    C. heat and momentum
    D. heat, momentum and mass
A

heat and mass

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4
Q
  1. A coalescer in a mixer-settler liquid-liquid extraction coloumn
    A. comprises of thin bed of substances of extended surface having high porosity.
    B. helps in increasing the bubble size entering the settler.
    C. helps in increasing the settling rate of the bubbles.
    D. all ‘a’, ‘b’, & ‘c’.
A

all ‘a’, ‘b’, & ‘c’.

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5
Q
  1. For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will
    A. increase
    B. decrease
    C. remain same
    D. data insufficient, can’t be predicted
A

increase

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6
Q
  1. Pick out the correct statement.
    A. 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.
    B. A sharp decrease in pressure drop is an indication of flooding in a distillation coloumn.
    C. Solvent used in extractive distillation should be of high volatility.
    D. Flash distillation is suitable for separating components which have very close boiling temperature.
A

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.

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7
Q
  1. 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
    A. vapour pressure of component A to that of component B.
    B. vapour pressure of component A to the total pressure.
    C. vapour pressure of component A to the partial pressure of A.
    D. partial pressure of component A to the total pressure.
A

vapour pressure of component A to that of component B.

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8
Q
  1. 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
    A. decoction
    B. percolation
    C. elutriation or elution
    D. none of these
A

elutriation or elution

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9
Q
  1. In the constant rate period of the rate of drying curve for batch drying,
    A. cracks develop on the surface of the solid.
    B. rate of drying decreases abruptly.
    C. surface evaporation of unbound moisture occurs.
    D. none of these.
A

surface evaporation of unbound moisture occurs.

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10
Q
  1. 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%).
    A. 15 min
    B. 51 min
    C. 71 min
    D. 94 min
A

71 min

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11
Q
  1. Agitator is provided in a crystalliser for
    A. avoiding deposition on cooler surfaces.
    B. formation of nuclei.
    C. crystal growth.
    D. all (a), (b) and (c).
A

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

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12
Q
  1. __________ diffusion is used for separating the isotopes of methane.
    A. Thermal
    B. Pressure
    C. Concentration
    D. Force
A

Thermal

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13
Q
  1. Ordinary diffusion process is also called __________ diffusion.
    A. pressure
    B. thermal
    C. concentration
    D. forced.
A

concentration

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14
Q
  1. Pick out the wrong statement.
    A. Different solids have different equilibrium moisture curves.
    B. Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column.
    C. Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
    D. Even a forced draft cooling tower can not cool water below the wet bulb temperature.
A

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

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15
Q
  1. Pick out the wrong statement pertaining to the rotary dryer.
    A. 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.
    B. 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.
    C. Rotary dryer is suitable for drying sticky material.
    D. Recommended peripherial speed of a rotary drier is in the range of 10 to 30 metres/minute.
A

Rotary dryer is suitable for drying sticky material.

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16
Q
  1. The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives
    A. low pressure drop and high hold up.
    B. high pressure drop and low hold up.
    C. low pressure drop and low hold up.
    D. high pressure drop and high hold up.
A

low pressure drop and low hold up.

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17
Q
  1. If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent.
    A. 100
    B. > 100
    C. < 100
    D. none of these
A

> 100

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18
Q
  1. 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
    A. 25%
    B. 50%
    C. 70%
    D. 90%
A

50%

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19
Q
  1. Raoult’s law is applicable to the
    A. ideal solutions
    B. real solutions
    C. mixture of water and alcohol
    D. non-ideal gases
A

ideal solutions

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20
Q
  1. Weeping in a distillation column
    A. increases tray efficiency.
    B. provides large interfacial surface for mass transfer.
    C. results due to very high gas velocity.
    D. results due to very low gas velocity.
A

results due to very low gas velocity.

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21
Q
  1. In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of
    A. area between operating line and 45° diagonal x-y diagram.
    B. condenser and reboiler surfaces.
    C. tower cross-section.
    D. none of these.
A

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

22
Q
  1. Wetted wall tower experiment determines the
    A. molal diffusivity.
    B. volumetric co-efficient.
    C. mass transfer co-efficient.
    D. none of these.
A

mass transfer co-efficient.

23
Q
  1. In McCabe-Thiele method, at infinite reflux ratio
    A. the overhead product is minimum.
    B. both the operating lines coincide with diagonal.
    C. both (a) and (b).
    D. neither (a) nor (b).
A

the overhead product is minimum.

24
Q
  1. With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency
    A. increases
    B. decreases
    C. remains same
    D. may increase or decrease ; depends on individual design
A

increases

25
Q
  1. Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the
    A. packing may be crushed due to thermal expansion/contraction of the components of the equipments.
    B. pressure drop in the equipment will be . very high.
    C. viscosity variation of the fluids may cause channeling/flooding.
    D. none of these.
A

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

26
Q
  1. The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is
    A. more
    B. less
    C. same
    D. either more or less; depends on the system
A

same

27
Q
  1. Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.
    A. wetted wall
    B. bubble cap
    C. perforated tray
    D. packed
A

wetted wall

28
Q
  1. Pick out the system with minimum boiling azeotrope at 1 atm.
    A. benzene-toluene
    B. ethyl alcohol-water
    C. hydrochloric acid-water
    D. all (a), (b) and (c)
A

ethyl alcohol-water

29
Q
  1. Free flowing granular materials can be best dried in a __________ drier.
    A. rotary
    B. cylinder
    C. drun
    D. freeze
A

rotary

30
Q
  1. In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction,
    A. inversely
    B. linearly
    C. exponentially
    D. none of these
A

linearly

31
Q
  1. Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number.
    A. Sherwood
    B. Schmidt
    C. Peclet
    D. Stanton
A

Sherwood

32
Q
  1. 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
    A. 0.31
    B. 0.107
    C. 0.017
    D. 0.215
A

0.215

33
Q
  1. Liquid diffusivity is of the order of __________ cm2 /second.
    A. 0.01
    B. 0.1
    C. 10^-5 to 10^-6
    D. > 1
A

10^-5 to 10^-6

34
Q
  1. The solvent used in liquid extraction should not have high latent heat of vaporisation, because
    A. the pressure drop and hence the pumping cost will be very high.
    B. it cannot be recovered by distillation.
    C. its recovery cost by distillation may be prohibitatively high.
    D. it will decompose while recovering by distillation.
A

its recovery cost by distillation may be prohibitatively high.

35
Q
  1. At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid __________ that in dry packed tower.
    A. is greater than
    B. is lower than
    C. is same as
    D. cannot be predicted as data are insufficient
A

is greater than

36
Q
  1. Molarity is defined as the number of gm moles of solute per __________ of solvent.
    A. litre
    B. kg
    C. gm
    D. c.c
A

litre

37
Q
  1. The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around
    A. 1
    B. 0.24
    C. 3.97
    D. 600
A

1

38
Q
  1. Which of the following T-H diagram is valid for dehumidification operation ?
A

A agad

39
Q
  1. 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)
    A. less number of trays are required.
    B. composition of the residue remains unchanged.
    C. more number of trays are required but the residue composition remains unchanged.
    D. more number of trays are required and the residue composition is more dilute in methanol.
A

less number of trays are required.

40
Q
  1. The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.
    A. exponential
    B. parabolic
    C. linear
    D. cubic
A

exponential

41
Q
  1. Which of the following binary systems is an example of a maximum boiling azeotrope ?
    A. Water-hydrochloric acid.
    B. Acetone-carbon disulphide.
    C. Water-ethyl alcohol.
    D. n-heptane-n-octane.
A

Water-hydrochloric acid.

42
Q
  1. (NRe . NSc) is termed in mass transfer operation as the __________ number.
    A. Stanton
    B. Sherwood
    C. Peclet
    D. none of these
A

Peclet

43
Q
  1. The binary diffusivity in gases and liquids vary respectively as
    A. T3/2 and T
    B. T and T3/2
    C. T and T3/2
    D. T3/2 and T
A

T^3/2 and T

44
Q
  1. Pick out the correct statement.
    A. The slope of the stripping line is always less than unity.
    B. 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.
    C. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.
    D. Kremsor-Brown-Souder’s equation is used to calculate the efficiency of a plate tower.
A

In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.

45
Q
  1. Pick out the correct statement.
    A. Dialysis process is used for the production of fresh water from brine.
    B. Electrodylsis is used in the manufacture of NaOH.
    C. Electrodylsis is used for the refin-ning/purification of petrol.
    D. both (b) and (c).
A

Electrodylsis is used in the manufacture of NaOH.

46
Q
  1. Pick out the correct statement.
    A. Bound moisture is removed during constant rate drying period.
    B. Free moisture is removed during falling rate drying period.
    C. The sum of free moisture and equilibrium moisture in a solid is called the critical moisture.
    D. The driving force for mass transfer in a wet solid is its free moisture content.
A

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

47
Q
  1. Very tall packed towers are divided into series of beds to
    A. reduce the overall pressure drop
    B. avoid channelling
    C. reduce liquid hold-up
    D. avoid flooding
A

avoid channelling

48
Q
  1. Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture.
    A. unbound
    B. free
    C. critical
    D. bound
A

free

49
Q
  1. With increase in temperature, the solubility of gases in liquids, at fixed pressure
    A. increases
    B. decreases
    C. remains same
    D. either (a) or (b), depends on the system
A

decreases

50
Q
  1. In most of the vacuum crystalliser, vacuum is generally produced by means of a
    A. suction pump
    B. compressed air jet
    C. steam jet ejector with a barometric condenser
    D. none of these
A

steam jet ejector with a barometric condenser

Philippine Chemical Engineering Licensure Examination Day 2 Separation Processes (14 decks)

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