Mass Transfer (Set 5)

Question 1

Which of the following parameters remains constant during chemical dehumidification?

Answer 1

Dry bulb temperature

Question 2

Drying of a solid involves ____ transfer.

Answer 2

both heat and mass

Question 3

Mechanism of moisture removal in case of freeze drying of food stuff is by

Answer 3

sublimation

Question 4

The dew point of an unsaturated gas-vapor mixture does not depend upon the ____ of the mixture.

Answer 4

temperature

Question 5

Which is not concerned directly with mass transfer?

Answer 5

Froude number

Question 6

Removal of ____ exemplifies an adsorption unit operation.

Answer 6

water from petrol

Question 7

Can the efficiency of a plate in the distillation tower be greater than 100%?

Answer 7

Never

Question 8

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.

Answer 8

increases

Question 9

For gas absorption, low viscosity solvents are preferred, because of their

Answer 9

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

Question 10

To remove all the moisture from a wet solid it requires exposure to ____ air.

Answer 10

perfectly dry

Question 11

The operating cost of a distillation column at minimum reflux ratio is

Answer 11

minimum

Question 12

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

Answer 12

2

Question 13

Molecular diffusivity of a liquid

Answer 13

increases with temperature.

Question 14

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.

Answer 14

> 25

Question 15

Henry’s law states that the

Answer 15

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

Question 16

Ammonia present in the coke oven gas is removed by washing with

Answer 16

dilute ammoniacal liquor

Question 17

With increase in temperature, the leaching rate increases due to

Answer 17

both (a) and (b)

Question 18

Which of the following processes is not an example of adsorption applied to gaseous separations?

Answer 18

Decolouration of yellow glycerene.

Question 19

The critical moisture content in case of drying indicates the ____ rate period.

Answer 19

beginning of falling

Question 20

Pick out the wrong statement

Answer 20

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 21

According to Poiseuille’s law, the permeability for gas flow through a capillary is proportional to (where, μ = gas viscosity)

Answer 21

1/μ

Question 22

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

Answer 22

1

Question 23

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

Answer 23

2

Question 24

Packed column distillation is limited to the column ____ metres.

Answer 24

both (a) & (b)

Question 25

For the flow of gases through a capillary, with increase in temperature, the permeability ____ as per Knudsen law.

Answer 25

increases

Question 26

Which of the following is directly concerned with psychrometry?

Answer 26

Lewis relationship

Question 27

Plate efficiency in a distillation column is reduced due to the ____ of liquid.

Answer 27

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

Question 28

The most efficient cooling tower out of the following is

Answer 28

induced draft

Question 29

Sodium bicarbonate is produced during soda ash manufacture using a ____ tower.

Answer 29

baffle

Question 30

Powdery materials can be guarded against caking tendency on storage by

Answer 30

none of these.

Question 31

In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the ____ number.

Answer 31

Lewis

Question 32

Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes?

Answer 32

Wetted wall columns

Question 33

The temperature of water cooled in cooling tower is always ____ temperature of entering air.

Answer 33

more than the wet bulb

Question 34

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?

Answer 34

Both heating and humidification

Question 35

Mass transfer co-efficient is directly proportional to DAB according to the ____ theory.

Answer 35

film

Question 36

The relative volatility of a binary mixture at constant temperature ____ the total pressure.

Answer 36

decreases with increase in

Question 37

Tower diameter may be decreased by

Answer 37

use of increased tray spacing.

Question 38

Rayleigh's equation applies to ____ distillation.

Answer 38

differential

Question 39

Steady state equimolal counter diffusion is encountered in

Answer 39

separation of a binary mixture by distillation.

Question 40

Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele's method?

Answer 40

Both (b) and (c)

Question 41

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?

Answer 41

Selectivity

Question 42

As the reflux ratio increases, the slope of the operating line for rectifying section

Answer 42

increases

Question 43

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)

Answer 43

log P vs . T

Question 44

The unit of volumetric diffusivity is

Answer 44

cm2/sec

Question 45

For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a ____ of the equilateral triangular co-ordinates.

Answer 45

pure component is represented by the apex.

Question 46

Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the ____ temperature.

Answer 46

wet-bulb

Question 47

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

Answer 47

10

Question 48

The slope of 9-line is determined by the

Answer 48

thermal condition of the feed

Question 49

In steam distillation, the

Answer 49

product must be immiscible with water.

Question 50

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?

Answer 50

Wet bulb temperature

Question 51

Steam distillation is used for separation of high boiling

Answer 51

both (a) and (b).

Question 52

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

Answer 52

increase

Question 53

Rose oil is extracted from rose leaves using ____ distillation.

Answer 53

steam

Question 54

Hypersorption refers to a ____ process.

Answer 54

moving bed adsorption

Question 55

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 55

https://www.indiabix.com/_files/images/chemical-engineering/mass-transfer/317-500-1.png

Question 56

Extraction of coffee from its seed is done by

Answer 56

leaching.

Question 57

In azeotropic mixture, the equilibrium vapour composition is

Answer 57

same as liquid composition.

Question 58

With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux

Answer 58

decreases

Question 59

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of

Answer 59

thermal diffusivity to mass diffusivity.

Question 60

According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity)

Answer 60

D

Question 61

Dry bulb temperature of the gas is ____ the wet bulb temperature.

Answer 61

more than

Question 62

Decoction refers to the use of solvent

Answer 62

at its boiling point

Question 63

Flash distillation is suitable for separating the constituents of a binary system, which

Answer 63

have very wide boiling points.

Question 64

The ratio of Murphree plate efficiency to point efficiency is 1 in a ____ flow model.

Answer 64

perfectly mixed

Question 65

The rough value of diffusion co-efficient of water vapor into air at 25°C may be about ____ cm2/sec.

Answer 65

0.25

Question 66

Flooding in a column results due to

Answer 66

high pressure drop

Question 67

Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty?

Answer 67

Wetted wall tower

Question 68

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?

Answer 68

The mixture exhibits an azeotrope at 101.3 kPa.

Question 69

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

Answer 69

and dehumidified with decrease in wet bulb temperature.

Question 70

The process employing desorption of the absorbed solute by a solvent is called

Answer 70

elution

Question 71

If the overall efficiency and Murphree plate efficiency are equal, then both the equilibrium and operating lines are

Answer 71

both (a) & (b)

Question 72

Which of the following operations does not involve leaching?

Answer 72

Removing nicotine from its water solution by kerosene.

Question 73

The recovery of pencillin from the acidified fermentation broth is done by

Answer 73

liquid extraction

Question 74

Unit operation involved in the prilling of urea is

Answer 74

both (b) and (c)

Question 75

Molecular seives are porous

Answer 75

synthetic zeolites crystals/metal alumino-silicates.

Question 76

Calcium ammonium nitrate (a fertiliser) is dried in a ____ dryer.

Answer 76

rotary

Question 77

A binary mixture of benzene and cyclohexane is separated by

Answer 77

extractive distillation

Question 78

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

Answer 78

there is equimolar counter diffusion.

Question 79

Cox chart is useful in the design of

Answer 79

distillation column

Question 80

Dew point of an air-water vapor mixture

Answer 80

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

Question 81

Can a cooling tower cool water below the wet bulb temperature of inlet air?

Answer 81

no

Question 82

The solvent used in liquid-liquid extraction should have ____ less than one.

Answer 82

neither (a) nor (b).

Question 83

The suitable evaporator for concentration of foaming liquids is a ____ evaporator.

Answer 83

long tube

Question 84

The ratio of Murphree plate efficiency to point efficiency is always > 1 in a ____ flow model.

Answer 84

plug

Question 85

Tea percolation employs

Answer 85

leaching

Question 86

Which of the following assumes constant molal vaporisation and overflow?

Answer 86

McCabe-Thiele method

Question 87

Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be

Answer 87

> 1

Question 88

Selectivity of the solvent used in solvent extraction should be

Answer 88

> 1

Question 89

Pick out the wrong statement pertaining to leaching.

Answer 89

Fine solids can not be leached in a Pachuka tank.

Question 90

Wet bulb and dry bulb temperatures becomes identical at ____ percent saturation curve.

Answer 90

100

Question 91

NSc/NPr is called the

Answer 91

Lewis number

Question 92

McCabe-Thiele method

Answer 92

uses molal units for material and energy balance.

Question 93

The film penetration model of mass transfer was enunciated by

Answer 93

Toor and Marchello

Question 94

The most economical range of absorption factor is

Answer 94

1.25 to 2

Question 95

Channelling is most severe

Answer 95

in towers packed with stacked packing.

Question 96

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

Answer 96

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

Question 97

ADDUCTS' and 'CLATHRATES' are used in case of

Answer 97

crystallisation.

Question 98

Adsorption is an unit operation which generally involves ____ systems.

Answer 98

fluid-solid

Question 99

In case of ____ distillation, a solvent is added to alter the relative volatility of the mixture to be separated.

Answer 99

extractive

Question 100

Separation of the isotopes of helium for scientific investigations is done by

Answer 100

thermal diffusion