Q.1

Use of natural draft cooling tower is practised, when the air has low

  • humidity
  • temperature
  • both 'a' & 'b'
  • neither 'a' nor 'b'
Q.2

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

  • minimum
  • infinite
  • optimum
  • none of these
Q.3

Design calculation for multiple component distillation is done by

  • Ponchon-Savarit method
  • Mccabe-Thiele method
  • enthalpy concentration method
  • tray to tray calculations.
Q.4

Mass transfer co-efficient is directly proportional to DAB0.5, according to __________ theory.

  • penetration
  • surface renewal
  • film
  • none of these
Q.5

In a packed bed absorption column, the channelling will be noted by the

  • increase in flow rate.
  • sharp drop in pressure drop.
  • sharp rise in pressure drop.
  • none of these.
Q.6

Sand is dried in foundaries in a___drier.

  • rotary
  • fluidisedbed
  • vacuum
  • spray
Q.7

If Rm is the minimum reflux ratio, the optimum reflux ratio may be around __________ Rm.

  • 1.2 to 1.5
  • 2.5 to 3
  • 3 to 4
  • 5
Q.8

Prandtl number for water at 20°C is about

  • 7
  • 70
  • 0.7
  • 150.
Q.9

Gaseous diffusivity at atmospheric pressure is of the order of __________ cm2/second.

  • 1
  • 1 to 5
  • 5 to 10
  • > 10
Q.10

In liquid-liquid extraction, the number of phases at plait point is

  • 1
  • 2
  • 3
  • 4
Q.11

The falling rate period in the drying of a solid is characterised by

  • increase in rate of drying.
  • increasing temperatures both on the surface and within the solid.
  • decreasing temperatures.
  • none of these.
Q.12

The rate of mass transfer is not dependent upon the

  • degree of dispersion of one fluid in the other.
  • interfacial surface exposed between the phases.
  • both (a) & (b).
  • none of these.
Q.13

Pressure drop through plate tower as compared to that through packed tower, for the same duty will be

  • less
  • more
  • equal
  • either (a) or (b); depends on the packing height
Q.14

Boiling point diagram is

  • not affected by pressure.
  • affected by pressure.
  • a plot of temperature vs. liquid composition.
  • a plot of temperature vs. vapour composition.
Q.15

Pick out the wrong statement.

  • In solvent extraction, the distribution co-efficient should be as large as possible for solvent economy.
  • With increase in pressure, the solubility of gases in solvent increases at a fixed temperature.
  • Decrease in Murphree plate efficiency is an indication of entrainment in distillation coloumn.
  • The capacity of a distillation coloumn is maximum at total reflux.
Q.16

The cooling effect in a cooling tower can not be increased by

  • increasing the air velocity over the wet surfaces.
  • reducing the humidity of entering air.
  • lowering the barometric pressure.
  • none of these.
Q.17

Which of the following employs an accessory known as 'drift eliminator' ?

  • Multiple effect evaporator.
  • Mechanical draft cooling tower.
  • Rotary dryer.
  • Rotating disc contactor.
Q.18

During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant.

  • wet bulb temperature
  • partial pressure of water vapor
  • relative humidity
  • none of these
Q.19

Pick out the wrong statement:

  • Absorption factor is constant, when the equilibrium and operating lines are straight.
  • In case of a stripper, the equilibrium curve is always below the operating line.
  • In case of an absorber, the operating line is always above the equilibrium curve.
  • In the absorption of low solubility gases, the liquid film is the controlling resistance.
Q.20

In a liquid-liquid extraction,kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact withkg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X, where Y* is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer.

  • The entire amount of C is transferred to solvent B.
  • Less than 2 kg but more than 1 kg of C is transferred to solvent B.
  • Less than 1 kg of C is transferred to B.
  • No amount of C is tranferred to B.
Q.21

In gas-liquid contact operation, the number of ideal stages, . This is true when the stripping factor 'S' is

  • S > 1
  • S < 1
  • S = 1
  • S = ∞
Q.22

In which of the following unit operations, the selectivity is an important parameter ?

  • Distillation
  • Solvent extraction
  • Absorption
  • None of these
Q.23

In gas-liquid contact operation, the number of ideal stages, . This is true when the stripping factor 'S' is

  • S > 1
  • S < 1
  • S = 1
  • S = ∞
Q.24

Dimension of mass diffusivity is the same as that of

  • kinematic viscosity
  • dynamic viscosity
  • surface tension
  • pressure
Q.25

When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30°C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system,

  • as the acetone concentration increases, the solubility curves approach each other.
  • both the phases become identical at a particular common point on both the solubility curves called the plait point.
  • the distribution curve which is a plot between x (acetone concentration in one phase) and y (acetone concentration in other phase) is analogous to x-y curve used in distillation and absorption terminates on the x = y diagonal at the concentration of the plait point.
  • all (a), (b) and (c).
Q.26

Steam distillation is used to

  • reduce the number of plates.
  • avoid thermal decomposition of a component.
  • increase the efficiency of separation.
  • increase the total pressure of distillation.
Q.27

For continuous drying of grannular or crystalline material, the dryer used is the __________ dryer.

  • tunnel
  • tray
  • rotary
  • none of these
Q.28

For contacting a highly soluble gas with a liquid

  • bubble the gas through liquid.
  • spray the liquid on gas stream.
  • either (a) or (b) would suffice.
  • none of these.
Q.29

The relative volatility of a binary mixture at the azeotropic composition is

  • 1
  • > 1
  • 0
  • ∞
Q.30

The value of NA/(NA + NB) for steady state molecular diffusion of gas 'A' through non-diffusing gas 'B' is

  • 1
  • ∞
  • 0.5
  • 2
Q.31

Pick out the correct statement.

  • Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas.
  • The 'Hatta number' is important in problems involving gas absorption without chemical reaction.
  • For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion.
  • Total reflux in case of distillation operation requires infinite number of plates for a binary system separation.
Q.32

In case of absorption, both the operating and equilibrium lines will be straight for

  • isothermal operation.
  • dilute solutions.
  • dilute solutions and isothermal operation.
  • none of these.
Q.33

In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as

Q.34

The surface renewal frequency in Danckwerts' model of mass transfer is given by (KL: mass transfer co-efficient)

  • KL2.DA
  • KL2.DA
  • KL2/DA
  • KL/DA2
Q.35

Which of the following is an undesirable characteristic for the solvent used in gas absorption ?

  • Low vapor pressure
  • Low viscosity
  • High gas solubility
  • None of these
Q.36

Dorr thickener is an equipment used for

  • classification
  • sedimentation
  • clarification
  • leaching
Q.37

Freundlich equation applies to the adsorption of solute from

  • dilute solutions, over a small concentration range.
  • gaseous solutions at high pressure.
  • concentrated solutions.
  • none of these.
Q.38

When adsorption hysteresis is observed, the desorption equilibrium pressure is __________ that obtained by adsorption.

  • always lower than
  • always higher than
  • same as
  • dependent on the system; can be either lower or higher than
Q.39

During drying operation, it is easier to remove the __________ moisture.

  • equilibrium
  • critical
  • unbound
  • bound
Q.40

With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas

  • increases
  • decreases
  • decreases linearly
  • remains unaffected
Q.41

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

  • only vapor phase follows Raoult's law.
  • only liquid phase obeys Dalton's law.
  • liquid phase obeys Dalton's law and vapor phase obeys Raoult's law.
  • Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.
Q.42

The humid volume may be increased by increasing the

  • temperature at constant humidity.
  • humidity at constant temperature.
  • both (a) and (b).
  • neither (a) nor (b).
Q.43

Pick out the correct statement.

  • For identical gas flow rates, less pressure drop occurs through a plate tower than through a packed tower.
  • Plate column can handle greater liquid loads without flooding than packed column, but the liquid hold up is more in the case of plate column.
  • For the same duty, plate columns weigh less than packed columns.
  • all (a), (b) and (c).
Q.44

Mass transfer co-efficient varies as DAB0.5, according to the __________ theory.

  • film
  • surface renewal
  • penetration
  • none of these
Q.45

Which of the following has the same dimension as mass diffusivity ?

  • Momentum flux
  • Kinematic viscosity
  • Thermal diffusivity
  • Both (b) and (c)
Q.46

Which of the following equipments is not used for liquid dispersion ?

  • Wetted wall towers
  • Packed towers
  • Venturi scrubbers
  • Agitated vessels
Q.47

Steam distillation is used to separate

  • azeotropes.
  • high boiling substances from nonvolatile impurities.
  • heat sensitive materials.
  • mixtures of low relative volatility.
Q.48

For ethanol-water system, the lowering of distillate quality fromtowill cause __________ plate requirement.

  • no change in theoretical
  • marginal decrease in the number of
  • major decrease in the number of
  • none of these
Q.49

Moisture in a substance exerting an equilibrium vapour pressure less than that of pure liquid at the same temperature is called the __________ moisture.

  • bound
  • unbound
  • critical
  • none of these
Q.50

Ion exchange process is similar to

  • absorption
  • adsorption
  • extraction
  • leaching
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