Q.1

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
Q.2

The Knudsen diffusivity is dependent on the

  • molecular velocity only.
  • pore radius of the catalyst only.
  • molecular mean free path only.
  • molecular velocity and por radius of the catalyst.
Q.3

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
Q.4

At what percentage (by volume) of alcohol composition, it forms an azeotrope with water ?

  • 90
  • 91.5
  • 95
  • 99
Q.5

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.
Q.6

Which of the following is not a continuous drier ?

  • Drum drier
  • Spray drier
  • Tunnel drier
  • Tray drier
Q.7

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
Q.8

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
Q.9

Milk is dried usually in a __________ dryer.

  • freeze
  • spray
  • tray
  • rotary
Q.10

The equation, is for

  • Fick's second law of diffusion.
  • stready state diffusion for stagnant case.
  • liquid M.T.C. by Higbie penetration theory.
  • none of these.
Q.11

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'
Q.12

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
Q.13

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

  • Yes
  • Normally not; but is possible if infinite number of plates are put.
  • Never
  • Yes ; if the reflux ratio is maximum.
Q.14

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.
Q.15

For a binary mixture distillation process, the degree of freedom isHowever, if the pressure is fixed in this process, the number of independent variables in this process will be

  • 1
  • 0
  • 2
  • 3
Q.16

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.to 0.mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y =+ 0.is

  • 2.0
  • 1.56
  • 1.0
  • 0.56
Q.17

The Reynolds number of the liquid was increasedfold 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
Q.18

The slope of 9-line is determined by the

  • reflux ratio
  • plate efficiency to be achieved
  • thermal condition of the feed
  • relative volatility.
Q.19

With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system)

  • increases
  • decreases
  • remains unaffected
  • increases Linearly
Q.20

With increase in temperature, the leaching rate increases due to

  • decreased liquid viscosity
  • increased diffusivity
  • both (a) and (b)
  • neither (a) nor (b)
Q.21

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.
Q.22

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
Q.23

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

  • minimum
  • maximum
  • infinite
  • zero
Q.24

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
Q.25

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
Q.26

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 containingmol% A and a bottom fraction containingmol% B ? Assume that relative volatility (αAB =does not change appreciably in the coloumn.

  • 5
  • 9
  • 12
  • 28
Q.27

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 m2/m3)

  • 500
  • 1200
  • 900
  • 800
Q.28

Large scale usage of flash distillation is practised in

  • soap manufacturing
  • ammonia synthesis plant
  • polymerisation industry
  • petroleum refinning
Q.29

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.
Q.30

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.
Q.31

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
Q.32

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
Q.33

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
Q.34

Which of the following is directly concerned with psychrometry ?

  • Lewis reltionship
  • Galileo number
  • Weber number
  • Dean number
Q.35

Packed column distillation is limited to the column __________ metres.

  • height < 6
  • diameter < 0.6
  • both (a) & (b)
  • neither (a) nor (b).
Q.36

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
Q.37

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.
Q.38

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

  • beginning of falling
  • beginning of constant
  • end of falling
  • none of these
Q.39

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

  • 2
  • 0.5
  • 50
  • 150
Q.40

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

  • increases
  • decreases
  • remains constant
  • data insufficient, cannot be predicted
Q.41

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).
Q.42

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
Q.43

During sensible cooling process

  • relative humidity decreases
  • relative humidity increases
  • wet bulb temperature decreases
  • both (b) and (c)
Q.44

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
Q.45

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
Q.46

Which of the following parameters remains constant during chemical dehumidifica-tion?

  • Dry bulb temperature
  • Partial pressure of vapour
  • Wet bulb temperature
  • None of these
Q.47

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.
Q.48

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).
Q.49

The equation, is for

  • Fick's second law of diffusion.
  • stready state diffusion for stagnant case.
  • liquid M.T.C. by Higbie penetration theory.
  • none of these.
Q.50

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

  • entrainment
  • foaming
  • weeping & dumping
  • all (a), (b) & (c)
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