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ChELE 2024 > IBX- Mass Transfer 7-9 > Flashcards

IBX- Mass Transfer 7-9 Flashcards

1
Q

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.

A

repeated coalescence & redispersion of the drop phase.

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2
Q

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’

A

interface

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3
Q

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.

A

Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.

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4
Q

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

A

-ve

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5
Q

The individual mass transfer co-efficients (moles/m2 . s) for absorption of a solute from a gas mixture into a liquid solvent are, KL = 4.5 and KG = 1.5. The slope of the equilibrium line is 3. Which of the following resistance (s) is (are) controlling ?

liquid side
gas side
interfacial
both liquid and gas side

A

gas side

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6
Q

Pore size of the molecular seive 5A is __________ mm.
5
0.5
0.05
50

A

0.5

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7
Q

Swenson-Walker crystalliser is a __________ unit
continuous
batch
semi-batch
cooling (adiabatic)-cum-evaporation

A

continuous

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8
Q

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 containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (αAB = 2) does not change appreciably in the coloumn.
5
9
12
28

A

12

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9
Q

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).

A

all (a), (b) and (c).

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10
Q

With increase in temperature, the mutual solubility of two liquids
increases
decreases
remains unchanged
decreases exponentially

A

increases

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11
Q

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.

A

The capacity of a distillation coloumn is maximum at total reflux.

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12
Q

The relative volatility of a binary mixture at the azeotropic composition is
1
> 1
0
∞

A

1

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13
Q

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.

A

Vapor phase obeys Dalton’s law and liquid phase obeys Raoult’s law.

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14
Q

Bound moisture is that liquid which exerts an equilibrium vapor pressure __________ that of the pure liquid at the given temperature.
less than
more than
equal to
either (o) or (b); depends on the solid

A

less than

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15
Q

Lewis number (Le) is
Sc / Pr
Pr x St
Sh x Pr
St x Sh

A

Sc / Pr

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16
Q

Which of the following is not a continuous leaching equipment ?
Pachuka tank
Kennedy extractor
Bollman extractor
Hydrocyclones

A

Pachuka tank

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17
Q

__________ extractor is used for the concentration of radioactive nuclear waste.
Pulsed column
Seive plate
Mixer-settler
Ballman

A

Pulsed column

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18
Q

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

A

equilibrium

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19
Q

All moisture in a non-hygroscopic material is the __________ moisture.
free
equilibrium
unbound
bound

A

unbound

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20
Q

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

A

(1 + Ro) = Ro/Ri

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21
Q

Separation of __________ employs gaseous diffusion process.
N2 and O2 from air
isotopes of uranium
isotopes of helium
SO2 and air

A

isotopes of uranium

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22
Q

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.

A

is computed from the slope of the upper operating line that is tangent to the equilibrium curve.

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23
Q

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

A

500

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24
Q

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

A

lower than

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25
Q

Experimental determination of __________ is done by wetted wall column method.
diffusion co-efficient
mass transfer co-efficient
NTU
none of these

A

mass transfer co-efficient

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26
Q

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.

A

In case of a stripper, the equilibrium curve is always below the operating line.

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27
Q

In liquid extraction, if the selectivity is unity, then
separation of the constituents is the most effective.
no separation will occur.
amount of solvent required will be minimum.
solvent flow rate should be very low.

A

no separation will occur.

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28
Q

Paper industry employs __________ driers.
cylinder
rotary
spray
fluidised bed

A

cylinder

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29
Q

Which of the following has the same dimension as mass diffusivity ?
Momentum flux
Kinematic viscosity
Thermal diffusivity
Both (b) and (c)

A

Both (b) and (c)

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30
Q

Pick out the wrong statement pertaining to the cooling towers.

In case of induced draft cooling tower, the fan is placed at the top of the tower.

Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air.

A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low.

Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

A

Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

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31
Q

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 = 0.01 respectively is

5.6 x 10-4
8.5 x 10-4
5.6 x 10-3
8.5 x 10-3

A

8.5 x 10-4

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32
Q

Leaching of coarse solid lumps is also termed as
decoction
dissolution
percolation
agitation and settling

A

percolation

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33
Q

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.

A

avoid channeling.

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34
Q

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

A

a pure substance

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35
Q

At what percentage (by volume) of alcohol composition, it forms an azeotrope with water ?
90
91.5
95
99

A

95

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36
Q

Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ coloumn.
spray
packed
bubble cap plate
wetted wall

A

wetted wall

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37
Q

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.

A

decreases.

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38
Q

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.

A

Co-efficient = Flux/concentration difference.

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39
Q

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.

A

the relative humidity decreases.

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40
Q

During sensible cooling process
relative humidity decreases
relative humidity increases
wet bulb temperature decreases
both (b) and (c)

A

both (b) and (c)

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41
Q

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

A

0

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42
Q

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.

A

equal to the heat of wetting.

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43
Q

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.

A

The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

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44
Q

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

A

1.25 to 2.0

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45
Q

Large scale usage of flash distillation is practised in
soap manufacturing
ammonia synthesis plant
polymerisation industry
petroleum refinning

A

petroleum refinning

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46
Q

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.

A

thermal decomposition of bottoms.

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47
Q

Alcohol is dehydrated using __________ distillation.
extractive
azeotropic
steam
molecular

A

azeotropic

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48
Q

Separation of two volatile liquids by distillation makes use of their
selectivity
relative volatility
solubility
density difference

A

relative volatility

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49
Q

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)

A

Both (b) and (c)

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50
Q

Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.
rotary
tray
freeze
none of these

A

tray

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51
Q

__________ is used as an ‘entrainer’ for the separation of acetic acid-water mixture by distillation.
Furfural
Benzol
Butyl acetate
Hexane

A

Butyl acetate

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52
Q

Rotary dryers cannot handle __________ materials.
free flowing
dry
sticky
grannular

A

sticky

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53
Q

Pick out the correct statement.

Diffusivity decreases with increase in temperature.
Diffusivity increases with increase in molecular weight.
Diffusivity increases with the size of the individual molecule.
none of these.

A

none of these.

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54
Q

An example of elutioh is
separation of uranium oxide from its ore by H2SO4 in a Pachuca tank.
separation of sugar from sugar beet by hot water.
dissolution of tannin out of tree barks by water.
recovery of vegetable oils from seeds.

A

separation of uranium oxide from its ore by H2SO4 in a Pachuca tank.

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55
Q

The operating line for an absorber is curved, when plotted in terms of
mole fractions
mole ratios
partial pressure
mass fractions

A

partial pressure

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56
Q

Relative volatility does not change appreciably with the change in

temperature
vapour pressure of either component
total pressure
none of these

A

temperature

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57
Q

Boiling point diagram is not affected by the ambient

pressure
humidity
temperature
both (b) and (c)

A

both (b) and (c)

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58
Q

The dew point of a saturated gas phase equals the __________ temperature.
gas
room
wet bulb
none of these

A

gas

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59
Q

A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process ?

Flow rate of inlet air
Relative humidity of outlet air
Humidity of inlet air
Temperature of the solid

A

Temperature of the solid

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60
Q

In case of liquid-liquid binary diffusion, diffusivity of one constituent into another is not dependent on the

temperature and pressure
concentration
nature of the constituents
none of these

A

none of these

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61
Q

For continuous drying of grannular or crystalline material, the dryer used is the __________ dryer.
tunnel
tray
rotary
none of these

A

rotary

62
Q

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

A

always lower than

63
Q

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

A

bound

64
Q

For a binary mixture with low relative volatility, continuous rectification to get pure products will require
low reflux ratio
less number of trays
small cross-section column
high reflux ratio

A

high reflux ratio

65
Q

The efficiency of a plate column will be maximum, when the flow is ideal __________ the plate.
across
above
both (a) & (b)
neither (a) nor (b)

A

both (a) & (b)

66
Q

Heat load in a cooling tower
means the amount of heat thrown away (KCal/hr.) by the cooling tower.
is equal to the number of kg, of water circulated times the cooling range.
both (a) & (b).
neither (a) nor (b).

A

both (a) & (b).

67
Q

In case of absorption with exothermic reaction, for fluids having

Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence.

Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same.

both (a) and (b)

Pr = Sc ; there won’t be any change in heat and mass transfer flux with changes in degree of turbulence.

A

both (a) and (b)

68
Q

Detergent solution is dried to a powder in a

spray dryer
spouted bed dryer
tunnel dryer
pan open to atmosphere

A

spray dryer

69
Q

Which of the following mixtures does not form an azeotrope at atmosheric pressure?
Water-alcohol
Methyl alcohol-acetone
Butyl acetate-water
None of these

A

None of these

70
Q

During bottling of cold drinks (e.g. Pepsi), the main resistance to mass transfer for the absorption of carbon dioxide in water lies in the
gas film
liquid film
liquid-gas interface
none of these

A

liquid film

71
Q

The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by

increasing the gas film co-efficient.
increasing the liquid film co-efficient.
increasing the total pressure.
decreasing the total pressure.

A

increasing the gas film co-efficient.

72
Q

Flooding results in
high tray efficiency
low tray efficiency
high gas velocity
good contact between the fluids

A

low tray efficiency

73
Q

For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because

water has a high latent heat of evaporation.
Lewis number is close to unity.
they are always equal under all circumstances.
solubility of the components of air in water is very small.

A

water has a high latent heat of evaporation.

74
Q

In an operating distillation column, the

vapors and liquids are at their dew point and bubble point respectively

driving force for the liquid flow is its specific weight.

driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.

highest temperature is encountered at the top of the column.

A

driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.

75
Q

In a forced draft cooling tower, water is cooled from 95 to 80°F by exposure to air with a wet bulb temperature of 70°F. In this case, the
range is 15°F.
approach is 10°F.
both (a) & (b).
neither (a) nor (b).

A

both (a) & (b).

76
Q

The diffusivity (D) in a binary gas mixture is related to the temperature (T) as
D ∝ T
D ∝ T^0.5
D ∝ T^1.5
D ∝ T^2

A

D ∝ T^1.5

77
Q

For which of the following unit operations, Lewis number is of significance ?
Adsorption
Binary distillation
Gas absorption
Humidification

A

Humidification

78
Q

Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches.
5
30
60
100

A

30

79
Q

If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement.
a1 = a2
a1 = 2a2
a1 = 0.5 a2
none of these

A

none of these

80
Q

The dimension of diffusivity is same as that of the
density
molal concentration
kinematic viscosity
velocity head

A

kinematic viscosity

81
Q

The temperature to which a vapour gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature.
dew point
wet bulb
dry bulb
none of these

A

none of these

82
Q

Entrainer used in azeotropic distillation should

form a low boiling azeotrope with one of the constituents of the mixture.
form a new azeotrope of low relative volatility with one of the constituents of the mixture.
have high latent heat of vaporisation.
have high viscosity to provide high tray efficiency.

A

form a low boiling azeotrope with one of the constituents of the mixture.

83
Q

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because

temperature is less.
total pressure is less.
mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.

saturated steam is used for steam distillation.

A

mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.

84
Q

Pick out the wrong statement.

The operating line always lies above the equilibrium solubility curve in case of a single component absorber.

The operating line always lies below the equilibrium solubility curve in case of a single component stripper.

The operating pressure in solvent extraction system should be below vapor pressures of all components.

The solubility of a particular gas in ideal solution in any solvent is always the same.

A

The operating pressure in solvent extraction system should be below vapor pressures of all components.

85
Q

Leaching of coffee from coffee beans is done by
hot water
hexane
lime water
dilute H2SO4 (hot)

A

hot water

86
Q

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.

A

bubble the gas through liquid.

87
Q

During drying operation, it is easier to remove the __________ moisture.
equilibrium
critical
unbound
bound

A

unbound

88
Q

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

A

decreases

89
Q

Ion exchange process is similar to
absorption
adsorption
extraction
leaching

A

adsorption

90
Q

A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state,

composition of vapors and that of liquid do not vary throughout the column.

reboiler load and condenser load are minimum.

the top and bottom compositions are unchanged with and without total reflux.

the top and bottom compositions correspond to the maximum enrichment available.

A

the top and bottom compositions correspond to the maximum enrichment available.

91
Q

Dryer widely used in a textile industry is __________ dryer.
festoon
cylinder
conveyor
tunnel

A

conveyor

92
Q

Solvent used in extractive distillation
changes the relative volatility of the original components.
should be of high volatility.
should form azeotropes with the original components.
all (a), (b) and (c)

A

changes the relative volatility of the original components.

93
Q

Air at a particular humidity is heated in a furnace. The new dew point
decreases
increases
depends on the extent of heating
remain unchanged

A

increases

94
Q

In a packed tower, the value of HETP equals HTUOG, when the equilibrium and the operating lines are (where, HETP = height equivalant to a theoretical plate HTUOG = overall gas phase height of a transfer unit)
straight
parallel
both (a) & (b)
neither (a) nor (b)

A

both (a) & (b)

95
Q

The vapour pressure exerted by the moisture contained in a wet solid depends upon the
nature of the moisture.
temperature.
nature of the solid.
all (a), (b) and (c).

A

all (a), (b) and (c).

96
Q

The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and, m = slope of the equilibrium line)

L/mG
G/mL
mL/G
LG/m

A

L/mG

97
Q

Smoke is an example of

solid dispersed in liquid
solid dispersed in gas
liquid dispersed in gas
gas dispersed in liquid

A

solid dispersed in gas

98
Q

Which of the following adsorbant is used in the refinning of sugar ?
Bone charcoal
Wood charcoal
Silica gel
Activated clay

A

Bone charcoal

99
Q

Stacked packing compared to dumped packing
provides poorer contact between the fluids.
gives lower pressure drop.
both (a) and (b).
gives higher pressure drop.

A

both (a) and (b).

100
Q

In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at __________ reflux.

total
minimum
operating
maximum permissible

A

total

101
Q

Which of the following parameters remains constant during chemical dehumidifica-tion?
Dry bulb temperature
Partial pressure of vapour
Wet bulb temperature
None of these parameters

A

Dry bulb temperature

102
Q

Drying of a solid involves __________ transfer.
only heat
only mass
both heat and mass
none of these

A

both heat and mass

103
Q

Mechanism of moisture removal in case of freeze drying of food stuff is by
evaporation
sublimation
dehydration
adsorption

A

sublimation

104
Q

The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture.
composition
temperature
total pressure
all (a), (b) and (c)

A

temperature

105
Q

Which is not concerned directly with mass transfer ?
Schmidt number
Sherwood number
Lewis relationship
Froude number

A

Froude number

106
Q

Removal of __________ exemplifies an adsorption unit operation.
uranium from its ore
water from petrol
ammonia from coke oven gas
mustard oil from mustard seed

A

water from petrol

107
Q

Can the efficiency of a plate in the distillation tower be greater than 100% ?
Yes
Normally not; but is possible if infinite number of plates are put.
Never
Yes ; if the reflux ratio is maximum.

A

Never

108
Q

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

A

increases

109
Q

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).

A

all (a), (b) and (c).

110
Q

To remove all the moisture from a wet solid it requires exposure to __________ air.
perfectly dry
highly humid
high temperature
none of these

A

perfectly dry

111
Q

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

A

minimum

112
Q

The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is
2
0.5
50
150

A

2

113
Q

Molecular diffusivity of a liquid
increases with temperature.
decreases with temperature.
may increase or decrease with temperature.
is independent of temperature.

A

increases with temperature.

114
Q

The wet and ‘dry bulb temperature for a vapour-gas mixture are 25°C and 30°C respectively. If the mixture is heated to 45°C at constant pressure, the wet bulb temperature will be __________ °C.
25
> 25
< 25
- 25

A

> 25

115
Q

Henry’s law states that the

partial pressure of a component over a solution is proportional to its mole fraction in the liquid.

partial pressure of a component over a solution is proportional to the mole fraction in the vapour.

vapour pressure is equal to the product of the mole fraction and total pressure.

partial pressure is equal to the product of the mole fraction and total pressure.

A

partial pressure of a component over a solution is proportional to its mole fraction in the liquid.

116
Q

Ammonia present in the coke oven gas is removed by washing with
caustic solution
dilute ammoniacal liquor
dilute HCl
ethanolamine

A

dilute ammoniacal liquor

117
Q

With increase in temperature, the leaching rate increases due to
decreased liquid viscosity
increased diffusivity
both (a) and (b)
neither (a) nor (b)

A

both (a) and (b)

118
Q

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.

A

Decolouration of yellow glycerene.

119
Q

The critical moisture content in case of drying indicates the __________ rate period.
beginning of falling
beginning of constant
end of falling
none of these

A

beginning of falling

120
Q

Pick out the wrong statement

A horizontal line on the humidity chart indicates the temperature changes at constant molal humidity.

When water is cooled from 80 to 70°C by exposure to the air with a wet bulb temperature of 60°C, then both the approach & the range would be 10°C.

For unsaturated air-water vapor mixture at atmospheric conditions, the wet bulb temperature & adiabatic cooling lines are the same.

Relative saturation of unsaturated mixture of water vapor & air can not be increased by either reducing the mixture temperature or by increasing the total pressure.

A

Relative saturation of unsaturated mixture of water vapor & air can not be increased by either reducing the mixture temperature or by increasing the total pressure.

121
Q

According to Poiseuille’s law, the permeability for gas flow through a capillary is proportional to (where, μ = gas viscosity)
μ
1/μ
sqrt (μ)
μ2

A

1/μ

122
Q

For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be
1
0
2
3

A

1

123
Q

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 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y = 5x + 0.001 is
2.0
1.56
1.0
0.56

A

2

124
Q

Packed column distillation is limited to the column __________ metres.
height < 6
diameter < 0.6
both (a) & (b)
neither (a) nor (b).

A

both (a) & (b)

125
Q

For the flow of gases through a capillary, with increase in temperature, the permeability __________ as per Knudsen law.
increases
decreases
remains same
either (a) or (b); depends on the gas

A

increases

126
Q

Which of the following is directly concerned with psychrometry ?
Lewis reltionship
Galileo number
Weber number
Dean number

A

Lewis reltionship

127
Q

Plate efficiency in a distillation column is reduced due to the __________ of liquid.
entrainment
foaming
weeping & dumping
all (a), (b) & (c)

A

all (a), (b) & (c)

128
Q

The most efficient cooling tower out of the following is
induced draft
forced draft
natural draft
atmospheric

A

induced draft

129
Q

Sodium bicarbonate is produced during soda ash manufacture using a __________ tower.
plate
baffle
packed
none of these

A

baffle

130
Q

Powdery materials can be guarded against caking tendency on storage by
providing irregular grain size.
providing minimum percentage of voids.
having maximum possible points of contact.
none of these.

A

none of these.

131
Q

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

A

Lewis

132
Q

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

A

Wetted wall columns

133
Q

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

A

more than the wet bulb

134
Q

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

A

Both heating and humidification

135
Q

Mass transfer co-efficient is directly proportional to DAB according to the __________ theory.
film
penetration
surface-renewal
none of these

A

film

136
Q

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

A

decreases with increase in

137
Q

Tower diameter may be decreased by
using higher reflux ratio.
use of increased tray spacing.
increasing the liquid flow rate.
increasing the vapour flow rate.

A

use of increased tray spacing.

138
Q

Rayleigh’s equation applies to __________ distillation.
continuous
steam
differential
flash

A

differential

139
Q

Steady state equimolal counter diffusion is encountered in
separation of a binary mixture by distillation.
absorption of NH3 from air by water.
all liquid-liquid diffusion systems.
all liquid-solid diffusion systems.

A

separation of a binary mixture by distillation.

140
Q

Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele’s method ?
Partial condenser
Total condenser
Reboiler
Both (b) and (c)

A

Both (b) and (c)

141
Q

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

A

Selectivity

142
Q

As the reflux ratio increases, the slope of the operating line for rectifying section
increases
decreases
remains constant
data insufficient, cannot be predicted

A

increases

143
Q

Cox chart, which is useful in the design of distillation column particularly for petroleum hydrocarbons, is a plot of (where, P = vapor pressure, T = temperature)
log P vs . T
log P vs. log T
T vs. P
P vs . log T

A

log P vs . T

144
Q

The unit of volumetric diffusivity is
cm2/sec
cm/sec
cm3/sec
cm2/sec2

A

cm2/sec

145
Q

For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates.

binary mixture is represented by the apex
binary mixture is represented by any point inside
ternery mixture is represented by the sides
pure component is represented by the apex.

A

pure component is represented by the apex.

146
Q

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

A

wet-bulb

147
Q

The Reynolds number of the liquid was increased 100 fold 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

A

10

148
Q

The slope of 9-line is determined by the
reflux ratio
plate efficiency to be achieved
thermal condition of the feed
relative volatility.

A

thermal condition of the feed

149
Q

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.

A

product must be immiscible with water.

150
Q

Which of the following can be calculated theoretically using steam table and Dalton’s law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known ?

Dew point
Humidity ratio
Wet bulb temperature
None of these

A

Wet bulb temperature

ChELE 2024 (17 decks)

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