Q.1

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

  • D
  • D2
  • D0.5
  • 1/D
Q.2

Unit operation involved in the prilling of urea is

  • evaporation
  • drying
  • crystallisation
  • both (b) and (c)
Q.3

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

  • reverse osmosis
  • thermal diffusion
  • leaching
  • solvent extraction
Q.4

L/mG is the expression for

  • absorption factor
  • Brinkman number
  • slope of operating line in absorber
  • slope of operating line in stripper.
Q.5

Cox chart is useful in the design of

  • distillation column
  • evaporator
  • dryer
  • crystalliser
Q.6

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

  • long tube
  • short tube
  • vacuum
  • falling film
Q.7

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.
Q.8

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.
Q.9

The film penetration model of mass transfer was enunciated by

  • Gilliland
  • Toor and Marchello
  • Stefan
  • Fick
Q.10

Molecular seives are porous

  • alumina.
  • silica.
  • synthetic zeolites crystals/metal alumino-silicates.
  • none of these.
Q.11

Extraction of pencillin employs a __________ extraction coloumn.

  • centrifugal
  • packed
  • plate
  • None of these.
Q.12

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'.
Q.13

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)
Q.14

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)
Q.15

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

  • elution
  • osmosis
  • reverse osmosis
  • sublimation
Q.16

The most economical range of absorption factor is

  • 0 to 0.5
  • 0 to 3
  • 1.25 to 2
  • 5 to 15
Q.17

In case of gases, the binary diffusivity is proportional to (where, P = pressure)

  • P
  • 1/P
  • 1/P
  • P
Q.18

Tea percolation employs

  • liquid-liquid extraction
  • leaching
  • absorption
  • none of these
Q.19

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

  • 0.25
  • 2.5
  • 1.25
  • 0.0025
Q.20

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.
Q.21

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.
Q.22

CO2 can be absorbed by

  • hot cupric oxide
  • heated charcoal
  • cold Ca(OH)2
  • alumina
Q.23

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
Q.24

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
Q.25

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.
Q.26

The Hatta number is important in

  • multicomponent distillation.
  • binary distillation.
  • gas absorption without chemical reaction.
  • gas absorption with chemical reaction.
Q.27

During drying of a solid, the critical moisture content increases with

  • decreased drying rate
  • increased thickness of the solid
  • increased drying rate
  • both (b) and (c).
Q.28

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
Q.29

As per Gilliland's equation, the diffusivity is

  • directly proportional to 'T1.5'.
  • inversely proportional to 'P'.
  • dependent on the molecular volume & molecular weight of components.
  • all 'a', 'b' & 'c'.
Q.30

For __________ drying, the effects of velocity, temperature and humidity of the gas and the thickness of the solid are the same.

  • unsaturated surface
  • constant rate
  • both (a) and (b)
  • neither (a) nor (b).
Q.31

Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the __________ number.

  • Schmidt
  • Sherwood
  • Peclet
  • Stanton
Q.32

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)
Q.33

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
Q.34

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.
Q.35

The commonly used solvent in supercritical extraction is

  • methyl ethyl ketone.
  • water.
  • carbon tetrachloride.
  • carbon dioxide.
Q.36

Coffee is prepared from coffee beans by leaching with

  • cold water
  • hot water
  • dilute hot caustic solution
  • naphtha
Q.37

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.
Q.38

What is the degree of freedom of an absorption process in which only one component is transferred between phases ?

  • 3
  • 2
  • 4
  • 1
Q.39

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).
Q.40

When the psychometric ratio is __________ then the adiabatic saturation temperature and wet bulb temperature becomes equal.

  • 1
  • < 1
  • > 1
Q.41

Flash distillation is

  • same as differential distillation.
  • used for multicomponent systems like crude refining.
  • same as simple distillation.
  • most useful for handling binary systems.
Q.42

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.
Q.43

Gaseous diffusion co-efficient increases with increase in the

  • pressure
  • temperature
  • both (a) & (b)
  • neither (a) nor (b)
Q.44

A mixture ofC6H6 vapour in air at 25°C andmm Hg has a dew point of 20°C. Its dew point at 30°C andmm Hg will be around __________ °C.

  • 21.7
  • 20
  • 27.3
  • 18.7
Q.45

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.
Q.46

Sticky material can be dried in a __________ dryer.

  • tray
  • rotary
  • fluidised bed
  • none of these
Q.47

Langmuir equation is associated with

  • leaching
  • adsorption
  • steam distillation
  • multicomponent absorption.
Q.48

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
Q.49

Desirable value of absorption factor in an absorber is

  • 1
  • < 1
  • > 1
  • 0.5
Q.50

__________ developed the film theory.

  • Higbie
  • Fick
  • Ergun
  • Levenspeil
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