Q.1

In a moderately sized packed absorption tower, channeling (which is most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter

  • > 4 :1
  • < 8 : 1
  • > 8:1
  • < 6:1
Q.2

Drift in a cooling tower is

  • the water entrained by the circulating air.
  • dependent on the water lost by evaporation.
  • desirable.
  • all (a), (b) & (c).
Q.3

__________ column is used in gas absorption process.

  • Wetted wall
  • Seive/perforated tray
  • Bubble cap
  • Packed
Q.4

JD factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by

  • Nsh = 2
  • Nst = 2
  • Nsc = 2
  • none of these
Q.5

Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the

  • mass transfer co-efficient.
  • thermal diffusivity.
  • kinematic viscosity.
  • volumetric diffusivity.
Q.6

Equilibrium moisture of a solid is equal to the total moisture minus free moisture. Which of the following substances will have maxi-mum equilibrium moisture ?

  • Anthracite coal
  • Rag paper
  • Bamboo
  • Inorganic solids
Q.7

When the solvent dissolves very little of solute, then

  • solvent of low latent heat of vaporisation should be used.
  • solvent of low freezing point should be used.
  • large quantity of solvent is required to extract the solute.
  • very small quantity of solvent is required.
Q.8

Molality is defined as the number of gm moles of solute per __________ of solvent.

  • litre
  • gm
  • Kg
  • m3
Q.9

For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams

  • increases
  • decreases
  • remains unaffected
  • passes through a maximum
Q.10

In case of unsaturated air

  • dew point < wet bulb temperature
  • wet bulb temperature < dry bulb temperature
  • both (a) and (b)
  • neither (a) not (b)
Q.11

In extraction, as the temperature increases, the area of hetrogeneity (area covered by binodal curve)

  • decreases
  • increases
  • remains unchanged
  • none of these
Q.12

Unit of molal diffusivity is

  • cm2/sec gm . mole
  • gm moles/cm2 . sec
  • gm moles/cm. sec
  • gm moles/cm2. sec
Q.13

Components, having widely different boiling point in a binary mixture, can be separated using __________ distillation.

  • molecular
  • extractive
  • steam
  • simple
Q.14

Pick out the wrong statement.

  • Mass transfer co-efficient does not account for gase-liquid diffusion.
  • Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation.
  • Contacting cold vapor-gas mixture with hot liquid exemplifies humidification process.
  • Contacting cold liquid with warm vapor-gas mixture exemplifies dehumidification process.
Q.15

Flash distillation is suitable for the separation of components

  • having very close boiling points.
  • which form maximum boiling azeotrope.
  • having very wide boiling points.
  • which form minimum boiling azeotrope.
Q.16

__________ is concerned with the adsorption equilibria.

  • Fick's law
  • Gibb's equation
  • Freundlich equation
  • none of these
Q.17

According to Chilton-Colburn analogy for mass transfer, NSt.NSc2/3 is equal to

  • f
  • f/2
  • 2f
  • 1/f
Q.18

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is

  • 0.54
  • 1.04
  • 1.24
  • 1.94
Q.19

Mass transfer co-efficient 'K' according to penetration theory varies with mass dif-fusivity as

  • D0.5
  • D
  • 1/D
  • D1.5
Q.20

If xD = overhead product molal composition and RD = reflux ratio, then slope and intercept of the operating line for rectifying section are respectively

Q.21

For a binary mixture with low relative volatility,

  • use steam distillation.
  • use molecular distillation.
  • use high pressure distillation.
  • an azeotrope may be formed during distillation.
Q.22

Pick out the wrong statement.

  • The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr = 1.
  • 1 Nm3 of dry air is lighter than 1Nm3 of humid air.
  • The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity.
  • An azeotropic mixture of two liquids has boiling point higher than either of them, when it shows negative deviation from Raoult's Law.
Q.23

Use of packed towers for distillation is generally limited to the

  • small sizes.
  • multicomponent distillation.
  • high pressure operation.
  • vacuum distillation.
Q.24

Molecular distillation is

  • high temperature distillation
  • for heat-sensitive materials
  • very low pressure distillation
  • both (b) and (c)
Q.25

The term "approach" in a cooling tower refers to the difference in the temperature of the

  • cold water leaving the tower and the wet bulb temperature of the surrounding air.
  • hot water entering the tower and the wet bulb temperature of the surrounding air.
  • hot water entering and the cooled water leaving the cooling tower.
  • none of these
Q.26

As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages

  • increase
  • decrease
  • remain unchanged
  • can either increase or decrease, depends on the system
Q.27

Which of the following equipments is not used in liquid-liquid extraction ?

  • Pachuka tank
  • Agitated vessels
  • Centrifugal extractors
  • Packed towers
Q.28

In rectifying section of a continuous distillation column, the

  • vapour is enriched with low boilers.
  • vapour is enriched with high boilers.
  • liquid is stripped of high boilers.
  • none of these.
Q.29

In Mcabe-Thiele method, at infinite reflux ratio

  • number of plates is maximum.
  • overhead product is maximum.
  • both the operating lines coincide with the diagram.
  • none of these.
Q.30

Fractional solvent extraction

  • employs only one solvent
  • employs two solvents
  • results in low interfacial tension
  • none of these
Q.31

In the layout plan for a vacuum distillation unit, operating atmm Hg, supported by a barometric condenser, the appropriate place for the location of vacuum drum for collecting the distillate will be

  • at ground level.
  • 2 metres above the ground.
  • 5 metres above ground.
  • 10 metres above ground.
Q.32

Minimum reflux ratio in a distillation column results in

  • optimum number of trays.
  • minimum reboiler size.
  • maximum condenser size.
  • minimum number of trays.
Q.33

Flooding in a distillation column is detected by a sharp

  • increase in Murphree plate efficiency.
  • decrease in pressure drop.
  • decrease in liquid hold up in the coloumn.
  • increase in pressure drop.
Q.34

Most important factor to be considered in the selection of packings for absorbers is the __________ of packing.

  • size
  • durability
  • porosity
  • cost
Q.35

Plate efficiency

  • is a function of the mass transfer between liquid and vapour.
  • increases due to foaming.
  • increases due to liquid entrainment.
  • increases due to weeping and dumping of liquid.
Q.36

Absorption accompanied by heat evolution results in

  • increased capacity of the absorber.
  • increase in equilibrium solubility.
  • decrease in equilibrium solubility.
  • none of these.
Q.37

In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation.

  • lower than
  • higher than
  • equal to
  • either (a) or (b), depends on the mixture composition
Q.38

Pick out the wrong statement.

  • The binary diffusivity in liquids is of the order of 10-5 cm2 /sec.
  • Molecular diffusion in solid is much faster than that in liquids.
  • Particles movement from higher concentration to lower concentration takes place in diffusion process.
  • According to Poiseuille's law, the permeability decreases with increase in temperature for flow of a gas through a given capillary.
Q.39

Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant

  • humidity
  • velocity
  • temperature
  • all (a), (b) & (c)
Q.40

Binary distillation involves the mass transfer by __________ at the gas-liquid interface.

  • unidirectional diffusion from liquid to gas phase
  • unidirectional diffusion from gas to liquid phase
  • either 'a' or 'b'
  • a counter diffusion at an almost equal molar rate
Q.41

In triangular co-ordinates, the ternery composition point falls __________ of the triangle.

  • in the corners
  • inside
  • on the sides
  • none of these.
Q.42

Pick out the wrong statement.

  • Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the possibility of tower wall collapse.
  • Packed towers are preferred over plate towers for handling corrosive and foamy liquids.
  • Diameter of randomly packed tower is normally more than 1.2 metres.
  • Due to uneven supply and improper distribution of liquid, problem of channeling, loading & flooding is generally encountered in packed towers.
Q.43

Leaching rate is independent of the

  • agitation
  • temperature
  • particle size
  • none of these
Q.44

__________ is the separation technique used for desalination of sea water.

  • Thermal diffusion
  • Reverse osmosis
  • Adsorption
  • absorption
Q.45

The relative saturation of a partially saturated mixture of vapour and gas can be increased by __________ of the mixture.

  • reducing the total pressure
  • increasing the total pressure
  • reducing the temperature
  • both (b) and (c)
Q.46

Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as

  • K ∝D
  • K ∝D
  • K ∝D1.5
  • K ∝D2
Q.47

Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the

  • high evaporation losses of water.
  • high pressure drop of the gas.
  • difficulty in its fabrication.
  • none of these.
Q.48

At 750°K and 1 atm, the approximate value of Schmidt number for air is

  • 0.01
  • 0.1
  • 1
  • 10
Q.49

When the solvent dissolves very little of solute, then

  • solvent of low latent heat of vaporisation should be used.
  • solvent of low freezing point should be used.
  • large quantity of solvent is required to extract the solute.
  • very small quantity of solvent is required.
Q.50

At constant pressure, with increase of temperature, the dew point will

  • increase
  • decrease
  • remain unchanged
  • increase/decrease ; depends on the temperature
0 h : 0 m : 1 s