Q.1

Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as

  • K ∝ D
  • K ∝D
  • K ∝ D1.5
  • K ∝ D2
Q.2

An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)

  • less number of trays are required.
  • composition of the residue remains unchanged.
  • more number of trays are required but the residue composition remains unchanged.
  • more number of trays are required and the residue composition is more dilute in methanol.
Q.3

With increase in temperature, the solubility of gases in liquids, at fixed pressure

  • increases
  • decreases
  • remains same
  • either (a) or (b), depends on the system
Q.4

The binary diffusivity in gases at atmospheric conditions is about

  • 10-9 cm/sec
  • 10-1 cm2/sec
  • 10-3 sec/cm
  • 10-4 cm2/sec2
Q.5

Bollman extractor

  • is a static bed leaching equipment.
  • is used for extraction of oil from oilseed.
  • is a centrifugal extractor.
  • employs only counter-current extraction.
Q.6

Pick out the wrong statement.

  • Different solids have different equilibrium moisture curves.
  • Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column.
  • Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
  • Even a forced draft cooling tower can not cool water below the wet bulb temperature.
Q.7

When the temperature and humidity of air is low, we usually use __________ draft cooling tower.

  • natural
  • forced
  • induced
  • none of these
Q.8

At minimum reflux ratio for a given separation

  • number of plates is zero.
  • number of plates is infinity.
  • minimum number of the theoretical plates is required.
  • separation is most efficient.
Q.9

In case of an absorber, the operating

  • line always lies above the equilibrium curve.
  • line always lies below the equilibrium curve.
  • line can be either above or below the equilibrium curve.
  • velocity is more than the loading velocity.
Q.10

Which of the following is the most suitable for extraction in a system having very low density difference ?

  • Mixer-settler extractor
  • Centrifugal extractor
  • Pulsed extractor
  • Packed extraction tower
Q.11

Pick out the correct statement.

  • Dialysis process is used for the production of fresh water from brine.
  • Electrodylsis is used in the manufacture of NaOH.
  • Electrodylsis is used for the refin-ning/purification of petrol.
  • both (b) and (c).
Q.12

The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.

  • exponential
  • parabolic
  • linear
  • cubic
Q.13

In most of the vacuum crystalliser, vacuum is generally produced by means of a

  • suction pump
  • compressed air jet
  • steam jet ejector with a barometric condenser
  • none of these
Q.14

Percentage saturation is __________ the relative saturation.

  • always smaller than
  • always greater than
  • not related to
  • none of these
Q.15

The relation, Sc = Pr =is valid, when the mechanism of __________ ansfer is same.

  • heat and mass
  • mass and momentum
  • heat and momentum
  • heat, momentum and mass
Q.16

As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches

  • that of normal condensation.
  • integral heat of adsorption.
  • zero.
  • none of these.
Q.17

For achieving rapid drying rate in a spray dryer, the diameter of the particles in the feed should be in the range of __________ microns (1 mm =microns).

  • 1-5
  • 10-60
  • 200-300
  • > 500
Q.18

A good solvent used for absorption should not have very high

  • viscosity
  • vapor pressure
  • freezing point
  • all (a), (b) & (c)
Q.19

Pick out the wrong statement pertaining to the rotary dryer.

  • Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12% of the inside diameter of shell.
  • Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.05 to 0.15.
  • Rotary dryer is suitable for drying sticky material.
  • Recommended peripherial speed of a rotary drier is in the range of 10 to 30 metres/minute.
Q.20

Positive deviation from Raoult's law means a mixture whose total pressure is

  • greater than that computed for ideality.
  • less than that computed for ideality.
  • less than the sum of the vapour pressure of the components.
  • none of these.
Q.21

In case of a desorber (stripper), the

  • operating line always lies above the equilibrium curve.
  • operating line always lies below the equilibrium curve.
  • temperature remains unaffected.
  • temperature always increases.
Q.22

Absorption factor method is used to calculate the number of ideal stages, when

  • operating line lies above the equilibrium line.
  • operating line lies below the equilibrium line.
  • both operating and equilibrium lines are parallel.
  • pressure drop in the column is very high.
Q.23

Pick out the wrong statement.

  • Critical moisture content is not a property of the material itself.
  • A sharp increase in pressure drop gives an indication of the flooding in a distillation column.
  • Separation of components is not possible in liquid extraction, if selectivity is unity.
  • Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.
Q.24

A minimum boiling azeotrope is exemplified by

  • toluene-benzene
  • acetone-carbon disulphide
  • water-isobutyl alcohol
  • none of these
Q.25

A coalescer in a mixer-settler liquid-liquid extraction coloumn

  • comprises of thin bed of substances of extended surface having high porosity.
  • helps in increasing the bubble size entering the settler.
  • helps in increasing the settling rate of the bubbles.
  • all 'a', 'b', & 'c'.
Q.26

At equilibrium the concentration of water in vapour phase (C*)in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially,kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is

  • 0.0
  • 0.2
  • 0.4
  • 1.0
Q.27

'Absorption with chemical reaction' is involved in the removal of

  • carbon dioxide from gaseous stream using alkaline solution.
  • benzol from coke oven gas using solar oil/wash oil.
  • ammonia from coke oven gas using refrigerated water.
  • tar from coke oven gas in primary gas coolers using chilled water.
Q.28

For absorbing a sparingly soluble gas in a liquid

  • gas side mass transfer co-efficient should be increased.
  • liquid side mass transfer co-efficient should be increased.
  • liquid side mass transfer co-efficient should be decreased.
  • mass transfer co-efficient must be kept constant.
Q.29

In a counter-current liquid extractor

  • both liquids flow at fixed rate.
  • both liquids can have any desired flow rate.
  • only one of the liquids may be pumped at any desired rate.
  • liquid's flow rate depends upon the temperature and pressure.
Q.30

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

  • increases
  • decreases
  • decreases linearly
  • remains unaffected
Q.31

On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in

  • greater degree of separation with a fixed number of trays
  • increased reboiler load
  • increased reflux ratio
  • None of these.
Q.32

What is the reflux ratio at total reflux ?

  • Zero
  • Infinity
  • Unity
  • Data insufficient
Q.33

Flights in a rotary dryer are provided to

  • lift and shower the solids thus exposing it thoroughly to the drying action of the gas.
  • reduce the residence time of solid.
  • increase the residence time of the solid.
  • none of these.
Q.34

Only small amount of evaporation of water produces large cooling effects because of its

  • large latent heat
  • low viscosity
  • small latent heat
  • none of these
Q.35

Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant.

  • agitated vessel
  • sieve tray column
  • bubble cap column
  • packed tower
Q.36

Which of the following solutions will follow Raoult's law most closely ?

  • A solution of benzene, toluene and oxylene.
  • 35% solution of camphor in water.
  • 35% solution of NH3 in water.
  • A solution of polar organic compounds (not of homologs of a series).
Q.37

The apex of an equilateral-triangular coordinate (in ternary liquid system) represents a/an

  • pure component
  • binary mixture
  • ternary mixture
  • insoluble binary system
Q.38

For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will

  • increase
  • decrease
  • remain same
  • data insufficient, can't be predicted
Q.39

Dry bulb temperature of unsaturated air is more than its __________ temperature.

  • dew point
  • wet bulb
  • both 'a' & 'b'
  • neither 'a' nor 'b'
Q.40

The-relative volatility for separation of a non-ideal binary mixture by distillation should be

  • 0
  • 1
  • > 1
  • < 1
Q.41

Channelling in a packed tower results from the

  • high pressure drop
  • maldistribution of liquid
  • non-uniformity of packing
  • both (b) and (c)
Q.42

Which of the following is an undesirable property for an absorbing solvent ?

  • Low vapour pressure
  • Low velocity
  • Low freezing point
  • None of these
Q.43

The caking of crystals can be prevented by

  • maintaining high critical humidity.
  • maintaining low critical humidity.
  • coating the product with inert material.
  • both (a) and (c)
Q.44

__________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids.

  • Watted wall
  • Packed
  • Plate
  • Spray
Q.45

Deairation (removal of O2) of water is done by

  • rectification
  • absorption
  • ion-exchange
  • adsorption
Q.46

Under conditions of flooding in packed tower, the gas pressure drop

  • decreases rapidly
  • increases rapidly
  • remains constant
  • is maximum
Q.47

The Kundsen diffusivity is proportional to (where, T = absolute temperature)

  • T
  • T2
  • T
  • T4
Q.48

Which of the following is an undesirable property in a tower packing ?

  • Large surface per unit volume.
  • Large free cross-section.
  • Low weight per unit volume.
  • Large weight of liquid retained.
Q.49

If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that

  • the system comprises of partially mis-cible liquids.
  • the system comprises of miscible liquids.
  • the system comprises of an azeotrope.
  • on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.
Q.50

The most common packing used in industrial operations is __________ rings.

  • raschig
  • lessing
  • cross-partition
  • single spiral
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