Q.1

High pressure at the bottom of a distillation tower handling heat sensitive materials results in

  • thermal decomposition of bottoms.
  • increased relative volatility.
  • erosion of the tower.
  • very efficient operation.
Q.2

Diameter to height ratio for a rashig ring is

  • 1
  • 0.5
  • 2
  • 8
Q.3

Which of the following is not a continuous leaching equipment ?

  • Pachuka tank
  • Kennedy extractor
  • Bollman extractor
  • Hydrocyclones
Q.4

Unsaturated air (with dry bulb and wet bulb temperatures being 45°C and 25°C respectively) is passed through a water spray chamber maintained at 23°C. The air will be cooled and

  • humidified with wet bulb temperature decreasing.
  • humidified at constant wet bulb temperature.
  • dehumidified.
  • none of these
Q.5

At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent.

  • 100
  • 0
  • 50
  • between 0 and 100
Q.6

Stage efficiency in a leaching process depends on the

  • time of contact between the solid and the solution
  • rate of diffusion of the solute through the solid and into the liquid
  • both (a) and (b)
  • vapour pressure of the solution
Q.7

Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 x 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.respectively is

  • 5.6 x 10-4
  • 8.5 x 10-4
  • 5.6 x 10-3
  • 8.5 x 10-3
Q.8

Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ coloumn.

  • spray
  • packed
  • bubble cap plate
  • wetted wall
Q.9

Diffusivity in concentrated solutions differs from that in dilute solutions, because of the changes in

  • viscosity with concentration.
  • degree of ideality of the solution.
  • both (a) and (b).
  • neither (a) nor (b).
Q.10

In physical terms, Schmidt number means

  • thermal diffusivity/mass diffusivity.
  • thermal diffusivity/momentum diffusivity.
  • momentum diffusivity/mass diffusivity.
  • mass diffusivity/thermal diffusivity.
Q.11

In case of liquids, the binary diffusivity is proportional to (where, T = temperature)

  • T
  • T
  • T2
  • 1/T
Q.12

Pick out the wrong statement.

  • The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one.
  • Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference.
  • According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(b)P - 3, Q - 2
  • The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz.
Q.13

Pick out the wrong statement.

  • In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed.
  • In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency.
  • For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10-2m/s. Then the average mass transfer co-efficient for the plate is 2 x 10-2m/s.
  • The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity.
Q.14

Heat sensitive materials like certain pharmaceuticals and food stuffs can be dried in a/an __________ dryer.

  • indirect tray
  • spray
  • freeze
  • none of these
Q.15

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.16

The percentage humidity is less than the relative humidity only at __________ percent humidity.

  • zero
  • hundred
  • both zero and hundred
  • none of these
Q.17

__________ equation applies to diffusivities in liquids.

  • Gilliland
  • Hirschfelder
  • Wilke and Chang
  • none of these
Q.18

Alcohol is dehydrated using __________ distillation.

  • extractive
  • azeotropic
  • steam
  • molecular
Q.19

Separation of two volatile liquids by distillation makes use of their

  • selectivity
  • relative volatility
  • solubility
  • density difference
Q.20

The equipment used in the extraction of highly corrosive radio active liquids is

  • pulse column
  • spray column
  • mixer settler
  • baffle tower
Q.21

__________ extractor is used for the concentration of radioactive nuclear waste.

  • Pulsed column
  • Seive plate
  • Mixer-settler
  • Ballman
Q.22

Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture.

  • free
  • unbound
  • equilibrium
  • bound
Q.23

Humid volume, at a given temperature is a/an __________ function of humidity.

  • inverse
  • exponential
  • linear
  • logarithmic
Q.24

Pore size of the molecular seiveis __________ mm.

  • 5
  • 0.5
  • 0.05
  • 50
Q.25

Separation of __________ employs gaseous diffusion process.

  • N2 and O2 from air
  • isotopes of uranium
  • isotopes of helium
  • SO2 and air
Q.26

In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is

  • equal to the heat of formation of surface compound.
  • equal to the heat of wetting.
  • zero.
  • called integral heat of adsorption.
Q.27

Operating velocity in a packed tower is usually __________ the flooding velocity.

  • half
  • twice
  • equal to
  • more than
Q.28

Leaching of coarse solid lumps is also termed as

  • decoction
  • dissolution
  • percolation
  • agitation and settling
Q.29

The main reason for dividing a tall packed tower into series of small towers is to

  • minimise the overall pressure drop.
  • avoid flooding.
  • reduce liquid hold up.
  • avoid channeling.
Q.30

With the lowering of equiliDrium pressure, at a given temperature, the amount of ad-sorbate on the adsorbent

  • increases.
  • decreases.
  • remains same.
  • either (a) or (b), depends on the system.
Q.31

Occurrence of 'case hardening' during drying of a high moisture solid cake __________ the drying rate.

  • increases
  • decreases
  • does not affect
  • exponentially increases
Q.32

In a distillation column, with increase in the reflux ratio, the heat removed in the cooler

  • increases.
  • decreases.
  • remains unaffected.
  • and the heat required in reboiler decreases.
Q.33

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.34

The diffusivity, DAB (for component A diffusing in B) is equal to the diffusivity DBA (for component B diffusing in A) for a binary mixture of

  • Newtonion liquids
  • non-Newtonion liquids
  • ideal gases
  • real gases
Q.35

In case of non-ideal gases and liquids, the molal diffusivity

  • varies inversely as the pressure.
  • varies directly as the pressure.
  • is independent of pressure.
  • is equal to the volumetric diffusivity.
Q.36

Back-trapping in a distillation column

  • increases tray efficiency.
  • decreases tray efficiency.
  • reduces pressure drop.
  • is desirable, as it provides improved vapour-liquid contact.
Q.37

Perforated plate towers are unique for solvent extraction because, they provide

  • higher contact area.
  • better contact of the phase.
  • repeated coalescence & redispersion of the drop phase.
  • none of these.
Q.38

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

  • Lewis
  • Grashoff
  • Sherwood
  • none of these
Q.39

Removal of __________ exemplifies an adsorption unit operation.

  • uranium from its ore
  • water from petrol
  • ammonia from coke oven gas
  • mustard oil from mustard seed
Q.40

Which of the following increases during evaporative cooling process with recirculated water supply ?

  • Wet bulb temperature
  • Relative humidity
  • Partial pressure of vapour
  • Both (b) and (c)
Q.41

Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.

  • rotary
  • tray
  • freeze
  • none of these
Q.42

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

  • μ
  • 1/μ
  • μ
  • μ2
Q.43

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

  • dry-bulb
  • wet-bulb
  • dew point
  • adiabatic saturation
Q.44

Advantage of continuous drying over batch drying is that the

  • drying cost per unit weight of dried product is less.
  • product with more uniform moisture content is produced.
  • equipment size required is smaller.
  • all 'a', 'b' & 'c'
Q.45

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

  • caustic solution
  • dilute ammoniacal liquor
  • dilute HCl
  • ethanolamine
Q.46

All moisture in a non-hygroscopic material is the __________ moisture.

  • free
  • equilibrium
  • unbound
  • bound
Q.47

The Schmidt number which is defined as, μ/ρ D, is the ratio of the

  • momentum diffusivity to the mass dif-fusivity.
  • thermal diffusivity to the mass diffusivity.
  • momentum diffusivity to the thermal diffusivity.
  • none of these.
Q.48

Swenson-Walker crystalliser is a __________ unit

  • continuous
  • batch
  • semi-batch
  • cooling (adiabatic)-cum-evaporation
Q.49

For water-ethanol system, the minimum reflux ratio

  • is computed from the slope of the upper operating line that is tangent to the equilibrium curve.
  • is computed from the intercept of the operating line.
  • cannot be computed.
  • is the optimum reflux ratio.
Q.50

Pick out the wrong statement:

  • Change in barometric pressure does not affect the relative humidity.
  • In case of a packed tower, the operating velocity is about half of the flooding velocity, generally.
  • 'Elution' means the desorption of the adsorbed solute by a solvent.
  • The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.
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