Heat Transfer

Question 1

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

Question 2

Separation of two or more components of a liquid solution cannot be achieved by a. liquid extraction b. absorption c. fractional crystallization d. evaporation b. absorption

Question 3

Solvent extraction is the terminology applied to the liquid-liquid extraction

Answer 3

which is preferred for the separation of the components of liquids

when a. extracting solvent is cheaply and abundantly available. b. one of the liquid components is heat sensitive. c. viscosity of liquid components is very high. d. one of the liquid components has very high affinity towards the solvent. d. one of the liquid components has very high affinity towards the solvent.

Question 4

The solvent used in liquid extraction should not have high latent heat of vaporization

Answer 4

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 prohibitively high. d. it will decompose while recovering by distillation. c. its recovery cost by distillation may be prohibitively high.

Question 5

Which of the following equipment is not used in liquid-liquid extraction? a. Pachuka tank b. Packed towers c. Agitated vessels d. Centrifugal extractors a. Pachuka tank

Question 6

Which of the following is an undesirable property for an absorbing solvent? a. Low vapor pressure b. Low freezing point c. Low viscosity d. None of these d. None of these

Question 7

Which method is more efficient

Answer 7

a single large washing or repeated small washing? a. single large washing b. repeated small washing c. either single large or repeated small washing d. none of these b. repeated small washing

Question 8

A solution of solute (A) in diluent (B) is mixed with solvent (S). The component (B) is slightly soluble in (S). The resulting extract will be a. rich in S

Answer 8

poor in B

poor in A b. poor in S

rich in B

poor in A c. rich in S

rich in B

rich in A d. rich in S

poor in B

rich in A rich in S

poor in B

rich in A

Question 9

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

Question 10

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

Question 11

In triangular coordinates

Answer 11

the ternary composition point falls __________ of the triangle. a. in the corners b. on the sides c. inside d. none of these c. inside

Question 12

The commonly used solvent in supercritical extraction is a. methyl ethyl ketone b. carbon tetrachloride c. water d. carbon dioxide d. carbon dioxide

Question 13

Which of the following equipment is NOT used for liquid dispersion? a. Wetted wall towers b. Packed tower c. Venturi scrubbers d. Agitated vessels d. Agitated vessels

Question 14

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

Question 15

The equipment used in the extraction of highly corrosive radioactive liquids is a. pulse column b. mixer settler c. spray column d. baffle tower a. pulse column

Question 16

Radioactive nuclear waste is treated in a. mixer-settler extractor b. rotating-disc contactor c. pulsed column extractor d. Bollman extractor c. pulsed column extractor

Question 17

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

Question 18

__________ extractor uses centrifugal force for separating the two phases. a. Treybal b. Podbielniak c. Schiebel d. none of these b. Podbielniak

Question 19

Desulfurization of petrol is done in a a. Bollman extractor b. rotating disc extractor c. packed extraction column d. plate type extraction column b. rotating disc extractor

Question 20

Which of the following is the most suitable for extraction in a system having very low-density difference? a. Mixer-settler extractor b. Centrifugal extractor c. Pulsed extractor d. Packed extraction tower b. Centrifugal extractor

Question 21

Which of the following solutions will follow Raoult’s law most closely? a. A solution of benzene

Answer 21

toluene and o-xylene b. 35% solution of camphor in water c. 35% solution of NH3 in water d. A solution of polar organic compounds (not of homologs of a series) a. A solution of benzene

toluene and o-xylene

Question 22

Boiling point diagram is a. not affected by pressure. b. affected by pressure. c. a plot of temperature vs. liquid composition. d. a plot of temperature vs. vapor composition b. affected by pressure.

Question 23

A 50 % by weight benzene - toluene mixture is fed to a column at 180 0F and 1 atm. The condition of the feed is called a. saturated liquid b. sub cooled liquid c. saturated vapor d. mixture of liquid and vapor b. sub cooled liquid

Question 24

The ease of difficulty of separating components by distillation is determined by the a. relative volatility b. viscosity c. mole fraction d. weight fraction of the components a. relative volatility

Question 25

When the liquid phase and vapor phase of a binary system obeys Raoult's and Dalton's law respectively

Answer 25

the relative volatility is the ratio of a. vapor pressure of component A to that of component B. b. vapor pressure of component A to the total pressure. c. vapor pressure of component A to the partial pressure of A. d. partial pressure of component A to the total pressure. a. vapor pressure of component A to that of component B.

Question 26

Relative volatility varies with the concentration of component for an ideal solution. The relative volatility of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B'

Answer 26

when a. only vapor phase follows Raoult's law. b. only liquid phase obeys Dalton's law. c. liquid phase obeys Dalton's law and vapor phase obeys Raoult's law. d. Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law. d. Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.

Question 27

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

Question 28

Liquid-liquid extraction is based on the differences in a. Solubility b. Specific volume c. Partial pressure d. Viscosity a. Solubility

Question 29

Heat sensitive materials with very high latent heat of vaporization may be economically separated using: a. Liquid extraction b. Distillation c. Evaporation d. Absorption a. Liquid extraction

Question 30

An ideal single stage extraction process is used to treat 100mol/s of an organic feed solution. The solute concentration in this solution is to be reduced from 0.5mol% to 0.1mol%. A pure solvent S is used. To reduce the solvent by half for the same separation

Answer 30

a. Add one more ideal co-current stage b. Use another pure solvent S* whose partition coefficient is twice that of S c. Use solvent S containing 0.02 mole fraction of the solute d. Double the residence time of the solvent S in the contactor b. Use another pure solvent S* whose partition coefficient is twice that of S

Question 31

The recovery of penicillin from the acidified fermentation broth is done by a) distillation b) evaporation c) absorption d) liquid extraction d) liquid extraction

Question 32

The solvent used in liquid-liquid extraction should have __________ less than one. a) selectivity b) distribution co-efficient c) both (a) and (b) d) neither (a) nor (b). d) neither (a) nor (b).

Question 33

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

Question 34

For a ternary mixture

Answer 34

in which equilateral triangular co-ordinate is used in leaching and extraction ## Footnote a __________ of the equilateral triangular co-ordinates. a) binary mixture is represented by the apex b) binary mixture is represented by any point inside c) ternary mixture is represented by the sides d) pure component is represented by the apex. d) pure component is represented by the apex.

Question 35

In liquid extraction

Answer 35

if the selectivity is unity ## Footnote then a) separation of the constituents is the most effective. b) no separation will occur. c) amount of solvent required will be minimum. d) solvent flow rate should be very low. b) no separation will occur

Question 36

In which of the following unit operations

Answer 36

the selectivity is an important parameter? a) Distillation b) Solvent extraction c) Absorption d) None of these b) Solvent extraction

Question 37

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

Question 38

What is the effect of entrainment carry-over of liquid droplets in the vapor flow to the tray above? A) Increases tray efficiency B) Causes a loss of tray efficiency C) Increases liquid flow rate D) Decreases vapor flow rate B) Causes a loss of tray efficiency

Question 39

How is the entrainment rate typically controlled in a distillation column? A) It is set to 100% of the liquid rate B) It is allowed at X% of the liquid rate based on company criteria C) It is set to a constant value regardless of the liquid rate D) It is directly proportional to the vapor flow rate B) It is allowed at X% of the liquid rate based on company criteria

Question 40

What happens during jet flooding in a distillation column? A) Liquid droplets move downward to the lower tray B) The spray or froth height reaches the tray above C) Vapor flow decreases drastically D) Tray efficiency improves significantly B) The spray or froth height reaches the tray above

Question 41

What is the primary consequence of jet flooding? A) Increased liquid flow to the lower tray B) Liquid no longer moves downward to the lower tray and pressure drop increases C) Vapor velocity decreases D) Tray efficiency improves B) Liquid no longer moves downward to the lower tray and pressure drop increases

Question 42

How can jet flooding be alleviated? A) Decrease tray spacing B) Increase tray spacing C) Decrease the liquid flow rate D) Increase the vapor flow rate B) Increase tray spacing

Question 43

At what liquid velocities does entrainment occur? A) Higher liquid velocities B) Lower liquid velocities C) Equal liquid and vapor velocities D) At very high vapor flow rates B) Lower liquid velocities

Question 44

At what liquid velocities does jet flooding occur? A) Lower liquid velocities B) Higher liquid velocities C) Moderate liquid velocities D) Equal liquid and vapor velocities B) Higher liquid velocities

Question 45

What happens during blowing in a distillation column? A) The tray operates with a high liquid load

Answer 45

and the tray is submerged in liquid B) The tray operates in the spray regime ## Footnote leading to massive entrainment of liquid to the tray above C) The tray deck is flooded with vapor only D) The liquid level is balanced and stable on the tray B) The tray operates in the spray regime leading to massive entrainment of liquid to the tray above

Question 46

What is the main cause of BLOWING in a distillation column? A) A high liquid-to-vapor ratio B) Very low liquid level on the tray C) High vapor flow rate D) Increased tray spacing B) Very low liquid level on the tray

Question 47

How can BLOWING be prevented in a distillation column? A) By increasing the height B) By increasing the liquid flow rate C) By decreasing the tray spacing D) By increasing the vapor flow rate A) By increasing the height

Question 48

Which of the following is the worst-case scenario of entrainment and jet flooding? A) Entrainment carry-over B) Jet flooding C) Blowing D) Tray flooding C) Blowing

Question 49

What condition is known as WEEPING in a distillation column? A) Liquid passes through the tray opening downwards due to high vapor velocity B) Liquid passes through the tray opening downwards due to low vapor velocity C) Liquid is forced up to the tray above due to high vapor velocity D) Liquid is trapped between two trays B) Liquid passes through the tray opening downwards due to low vapor velocity

Question 50

What is the primary cause of weeping in a distillation column? A) High vapor velocity through the tray opening B) Low vapor velocity through the tray opening C) High liquid-to-vapor ratio D) Increased tray spacing B) Low vapor velocity through the tray opening

Question 51

How is weeping typically controlled? A) By optimizing the number of holes or hole size in the tray B) By increasing the liquid flow rate C) By increasing the tray spacing D) By decreasing the vapor flow rate A) By optimizing the number of holes or hole size in the tray

Question 52

What is the weeping criterion in terms of liquid rate? A) 10% of the liquid rate B) 15% of the liquid rate C) 20% of the liquid rate as turn down D) 25% of the liquid rate as turn down C) 20% of the liquid rate as turn down

Question 53

What is the condition called when 90% or more of the liquid passes through the tray holes? A) Weeping B) Jet flooding C) Dumping D) Blowing C) Dumping

Question 54

What causes dumping in a distillation column? A) Vapor flow rate is too high B) Vapor flow rate is too low C) High liquid flow rate D) Low liquid flow rate B) Vapor flow rate is too low

Question 55

What happens in the worst-case scenario of dumping? A) No vapor exits the top of the column B) No liquid comes from the outlet weir C) Liquid is trapped in the column D) The liquid phase becomes too concentrated B) No liquid comes from the outlet weir

Question 56

When does weeping occur in relation to liquid velocity? A) At higher liquid velocities B) At lower liquid velocities C) When liquid and vapor velocities are equal D) When liquid flow is balanced with vapor flow A) At higher liquid velocities

Question 57

When does dumping occur in relation to liquid velocity? A) At higher liquid velocities B) At lower liquid velocities C) When liquid and vapor velocities are equal D) When liquid flow is increased B) At lower liquid velocities

Question 58

"What is the ""system limit"" in the context of a distillation column? A) The condition where the liquid droplets are too large to be carried by the vapor B) When the vapor velocity exceeds the terminal velocity of the liquid droplets, causing the liquid to be carried upward C) The maximum vapor flow rate a column can handle without flooding D) The maximum liquid flow rate a column can handle before overflowing" B) When the vapor velocity exceeds the terminal velocity of the liquid droplets

Answer 58

causing the liquid to be carried upward

Question 59

What is the solution when the system limit is reached in a distillation column? A) Increase the vapor flow rate B) Increase the tray diameter C) Increase the number of trays D) Decrease the liquid flow rate B) Increase the tray diameter

Question 60

Does the system limit depend on tray construction? A) Yes

Answer 60

it depends on the specific tray design used B) No ## Footnote it only depends on the tower diameter C) Yes it depends on the internal adjustments in the column D) No it is not affected by the tray design at all B) No it only depends on the tower diameter