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DAY 2 > Mass Transfer Part 3 > Flashcards

Mass Transfer Part 3 Flashcards

1
Q

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

A

Dry bulb temperature

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2
Q

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

A

both heat and mass

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3
Q

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

A

sublimation

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4
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

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5
Q

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

A

Froude number

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6
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

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7
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

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8
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

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9
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).

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10
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

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11
Q

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

A

minimum

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12
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

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13
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.

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14
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

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15
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.

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16
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

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17
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)

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18
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.

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19
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

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20
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.

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21
Q

According to Poiseuille’s law, the permeability for gas flow through a capillary is proportional to (where, u = gas viscosity)
u
1/u
sqrt(u)
u^2

A

1/u

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22
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

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23
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
1.56
1
0.56

A

2

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24
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)

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25
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

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26
Q

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

A

Lewis relationship

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27
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)

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28
Q

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

A

induced draft

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29
Q

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

A

baffle

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30
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.

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31
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

Lewis ratio of heat and mass transfer

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32
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

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33
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

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34
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

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35
Q

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

A

film

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36
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

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37
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.

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38
Q

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

A

differential

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39
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.

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40
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)

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41
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

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42
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

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43
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

Cox logP T

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44
Q

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

A

cm2/sec

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45
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.

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46
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

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47
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

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48
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

9-line thermal condition

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49
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.

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50
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

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51
Q

Steam distillation is used for separation of high boiling substances from
non-volatile impurities.
volatile impurity from still higher boiling substances.
both (a) and (b).
neither (a) nor (b).

A

both (a) and (b).

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52
Q

The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will
increase
decrease
remains same
depend on saturated boiling point; may increase or decrease

A

increase

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53
Q

Rose oil is extracted from rose leaves using __________ distillation.
high pressure
low pressure
extractive
steam

A

steam

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54
Q

Hypersorption refers to a __________ process.
fixed bed absorption
moving bed absorption
fixed bed adsorption
moving bed adsorption

A

moving bed adsorption

hypersorption moving bed aDsorption

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55
Q

Extraction of coffee from its seed is done by
liquid-liquid extraction.
leaching.
extractive distillation.
steam distillation.

A

leaching.

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56
Q

In azeotropic mixture, the equilibrium vapour composition is
more than liquid composition.
less than liquid composition.
same as liquid composition.
independent of pressure.

A

same as liquid composition.

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57
Q

With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux
increases
decreases
remains same
may increase or decrease ; depends on system.

A

decreases

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58
Q

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of
mass diffusivity to momentum diffusivity.
thermal diffusivity to mass diffusivity.
momentum diffusivity to thermal diffusivity.
none of these.

A

thermal diffusivity to mass diffusivity.

LTM Lewiss Thermal to Mass

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59
Q

According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity)
D
D^2
D^0.5
1/D

A

D

film theory D

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60
Q

Dry bulb temperature of the gas is __________ the wet bulb temperature.
less than
more than
equal to
none of these

A

more than

61
Q

Decoction refers to the use of solvent
at ambient temperature
at its boiling point
in its vapor form
none of these

A

at its boiling point

DBP Decoction boiling point

62
Q

Flash distillation is suitable for separating the constituents of a binary system, which
form minimum boiling azeotrope.
have very wide boiling points.
have very close boiling points.
form constant boiling azeotrope.

A

have very wide boiling points.

63
Q

The ratio of Murphree plate efficiency to point efficiency is 1 in a __________ flow model.
plug
perfectly mixed
both (a) & (b)
neither (a) nor (b)

A

perfectly mixed

64
Q

The rough value of diffusion co-efficient of water vapor into air at 25 C may be about __________ cm2/sec.
0.25
2.5
1.25
0.0025

A

0.25

65
Q

Flooding in a column results due to
high pressure drop
low pressure drop
low velocity of the liquid
high temperature

A

high pressure drop

66
Q

Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty?
Grid tray tower
Perforated tray tower
Wetted wall tower
Bubble cap tower

A

Wetted wall tower

67
Q

A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture?
The mixture exhibits an azeotrope at 101.3 kPa.
The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10.
The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10.
The mixture contain optical isomers.

A

The mixture exhibits an azeotrope at 101.3 kPa.

68
Q

Unsaturated air (with dry bulb temperature and dew point being 35 C and 18 C respectively) is passed through a water spray chamber maintained at 15 C. The air will be cooled
and humidified.
and dehumidified with increase in wet bulb temperature.
at the same relative humidity.
and dehumidified with decrease in wet bulb temperature.

A

and dehumidified with decrease in wet bulb temperature.

69
Q

The process employing desorption of the absorbed solute by a solvent is called
elution
osmosis
reverse osmosis
sublimation

A

elution

desorption by solvent elution

70
Q

If the overall efficiency and Murphree plate efficiency are equal, then both the equilibrium and operating lines are
straight
parallel
both (a) & (b)
neither (a) nor (b)

A

both (a) & (b)

71
Q

Which of the following operations does not involve leaching?
Dissolving gold from ores.
Dissolving pharmaceutical products from bark or roots.
Dissolving sugar from the cells of the beet.
Removing nicotine from its water solution by kerosene.

A

Removing nicotine from its water solution by kerosene.

72
Q

The recovery of pencillin from the acidified fermentation broth is done by
distillation
evaporation
absorption
liquid extraction

A

liquid extraction

73
Q

Unit operation involved in the prilling of urea is
evaporation
drying
crystallisation
both (b) and (c)

A

both (b) and (c)

74
Q

Molecular seives are porous
alumina.
silica.
synthetic zeolites crystals/metal alumino-silicates.
none of these.

A

synthetic zeolites crystals/metal alumino-silicates.

75
Q

Calcium ammonium nitrate (a fertiliser) is dried in a __________ dryer.
rotary
vacuum
tunnel
tray

A

rotary

fertiliser rotary

76
Q

A binary mixture of benzene and cyclohexane is separated by
flash vaporisation
extractive distillation
solvent extraction
ordinary distillation

A

extractive distillation

77
Q

Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular difusion, if
mass transfer is accompanied by reaction.
diffusion of A is in stagnant medium B.
molecular mean free path is high.
there is equimolar counter diffusion.

A

there is equimolar counter diffusion.

78
Q

Cox chart is useful in the design of
distillation column
evaporator
dryer
crystalliser

A

distillation column

79
Q

Dew point of an air-water vapor mixture
decreases with decrease in pressure.
at constant humidity & total pressure is fixed.
corresponding to any point on the humidity chart is obtained by projecting a line through this point parallel to the temperature axis and to the saturation curve.
all ‘a’, ‘b’ & ‘c’.

A

all ‘a’, ‘b’ & ‘c’.

80
Q

Can a cooling tower cool water below the wet bulb temperature of inlet air?
yes
no
yes ; but height of cooling tower will be prohibitively high.
yes ; but the air flow rate should be excessively high.

A

no

81
Q

The solvent used in liquid-liquid extraction should have __________ less than one.
selectivity
distribution co-efficient
both (a) and (b)
neither (a) nor (b).

A

neither (a) nor (b).

82
Q

The suitable evaporator for concentration of foaming liquids is a __________ evaporator.
long tube
short tube
vacuum
falling film

A

long tube

83
Q

The ratio of Murphree plate efficiency to point efficiency is always > 1 in a __________ flow model.
plug
perfectly mixed
both (a) & (b)
neither (a) nor (b)

A

plug

84
Q

Tea percolation employs
liquid-liquid extraction
leaching
absorption
none of these

A

leaching

85
Q

Which of the following assumes constant molal vaporisation and overflow?
McCabe-Thiele method
Ponchan-Savarit method
Enthalpy concentration method
Plate absorption column

A

McCabe-Thiele method

86
Q

Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be
1
> 1
< 1
? 1

A

> 1

87
Q

Selectivity of the solvent used in solvent extraction should be
1
> 1
< 1
0

A

> 1

88
Q

Pick out the wrong statement pertaining to leaching.
Fine solids can not be leached in a Pachuka tank.
Door classifier can be used for leaching of coarse solids.
Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor.
Very high temperature is not needed for the leaching of sugar beet.

A

Fine solids can not be leached in a Pachuka tank.

89
Q

Wet bulb and dry bulb temperatures becomes identical at __________ percent saturation curve.
100
50
78
none of these

A

100

90
Q

NSc/NPr is called the
psychrometric ratio
Lewis number
Sherwood number
Stantan number

A

Lewis number

91
Q

McCabe-Thiele method
uses molal units for material and energy balance.
uses weight fractions to express liquid and vapour composition.
can use any type of units.
is more accurate than Ponchan-Savarit method.

A

uses molal units for material and energy balance.

92
Q

The film penetration model of mass transfer was enunciated by
Gilliland
Toor and Marchello
Stefan
Fick

A

Toor and Marchello

93
Q

The most economical range of absorption factor is
0 to 0.5
0 to 3
1.25 to 2
5 to 15

A

1.25 to 2

94
Q

Channelling is most severe
in towers packed with stacked packing.
in towers packed randomly with crushed solids.
in dumped packing of regular units.
at very high liquid flow rate.

A

in towers packed with stacked packing.

95
Q

Out of two equilibrium curves, first one lies above the diagonal and the second lies below the diagonal in the x-y plot. It means that separation by distillation is
not possible in the second case unless vacuum is applied.
not possible in the second case unless high pressure is applied.
more readily done in the second case compared to first one.
none of these

A

more readily done in the second case compared to first one.

out of two… more readily done..

96
Q

ADDUCTS’ and ‘CLATHRATES’ are used in case of
extractive distillation.
crystallisation.
absorption.
none of these.

A

crystallisation.

ACC ADDUCTS CLATHRATES CRYSTALLISATION

97
Q

Adsorption is an unit operation which generally involves __________ systems.
liquid-solid
gas-solid
fluid-solid
solid-solid

A

fluid-solid

98
Q

In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated.
molecular
azeotropic
extractive
flash.

A

extractive

99
Q

Separation of the isotopes of helium for scientific investigations is done by
reverse osmosis
thermal diffusion
leaching
solvent extraction

A

thermal diffusion

isotopes thermal diffusion

100
Q

In a binary system, separation is very efficient, when the relative volatility is
1
> 1
< 1
0.5

A

> 1

101
Q

Fenske-Underwood equation used for calculating the minimum number of theoretical plates in distillation column is valid for
constant molal overflow
total reflux
constant relative volatility
all (a), (b) and (c)

A

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

102
Q

The binary diffusivity in gases does not depend upon the
pressure
temperature
nature of the components
none of these

A

none of these

103
Q

Berl saddle made of carbon cannot be used for
alkalis
SO2
H2SO4
oxidising atmosphere

A

oxidising atmosphere

berl cannot oxidising atmosphere

104
Q

1 kg of a saturated aqueous solution of a highly soluble component A at 60 C is cooled to 25 C. The solubility limits of A are (0.6 kgA/kg water) at 60 C and (0.2 kgA/kg water) at 25 C. The amount in kg of the crystals formed is
0.4
0.25
0.2
0.175

A

0.2

105
Q

During drying of a solid, the critical moisture content increases with
decreased drying rate
increased thickness of the solid
increased drying rate
both (b) and (c).

A

both (b) and (c).

106
Q

Priming in a distillation column
results from very low gas velocity.
is desirable from point efficiency consideration.
is characterised by the presence of foam throughout the space between trays.
reduces the overall pressure drop.

A

is characterised by the presence of foam throughout the space between trays.

107
Q

The commonly used solvent in supercritical extraction is
methyl ethyl ketone.
water.
carbon tetrachloride.
carbon dioxide.

A

carbon dioxide.

108
Q

When the liquid over a plate is of uniform concentration, then
Murphree efficiency > point efficiency.
Murphree efficiency < point efficiency.
Murphree efficiency = point efficiency.
Murphree efficiency ≠ point efficiency.

A

Murphree efficiency = point efficiency.

109
Q

In saturated gas, the
vapour is in equilibrium with the liquid at the gas temperature.
vapour is in equilibrium with the liquid at the room temperature.
partial pressure of vapour equals the vapour pressure of the liquid at room temperature.
none of these.

A

vapour is in equilibrium with the liquid at the gas temperature.

110
Q

As per Gilliland’s equation, the diffusivity is
directly proportional to ‘T1.5’.
inversely proportional to ‘P’.
dependent on the molecular volume & molecular weight of components.
all ‘a’, ‘b’ & ‘c’.

A

all ‘a’, ‘b’ & ‘c’.

111
Q

Pick out the wrong statement.
When the concentration difference for the mass transfer becomes zero at the bottom of the gas absorption tower, then the upper end of the operating line touches the equilibrium curve.
The average distance between the operating line and equilibrium line is large, when the liquid-gas ratio is also large in case of a counter current gas absorption tower.
The operating line lies above the equilibrium curve in case of a gas desorber.
With decrease in the liquid flow rate for a fixed gas flow rate, the slope of the operating line decreases, in case of gas absorption process.

A

The operating line lies above the equilibrium curve in case of a gas desorber.

112
Q

A mixture of 10% C6H6 vapour in air at 25 C and 750 mm Hg has a dew point of 20 C. Its dew point at 30 C and 700 mm Hg will be around __________ C.
21.7
20
27.3
18.7

A

18.7

113
Q

Which of the following is not fixed by the process requirements, in the design of absorbers?
Flow rate of the entering gas.
Composition of the entering liquid.
Terminal concentrations of gas stream.
None of these.

A

None of these.

114
Q

If the amount of the steam used in steam distillation is increased, the temperature of distillation
increases
decreases
remains unchanged
depends on relative volatility

A

decreases

115
Q

Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture.
unbound
critical
free
bound

A

unbound

116
Q

Inside the distillation columns, the
highest temperatures is near the feed plate.
driving force for the liquid flow is its weight.
vapors are not always at their dew points.
all (a), (b) and (c)

A

driving force for the liquid flow is its weight.

117
Q

When the psychometric ratio is __________ then the adiabatic saturation temperature and wet bulb temperature becomes equal.
1
< 1
> 1
infinite

A

1

118
Q

Desirable value of absorption factor in an absorber is
1
< 1
> 1
0.5

A

> 1

119
Q

Refractory bricks are usually dried in a __________ dryer.
tray
tunnel
conveyor
festoon

A

tunnel

tunnel refractory

120
Q

For __________ drying, the effects of velocity, temperature and humidity of the gas and the thickness of the solid are the same.
unsaturated surface
constant rate
both (a) and (b)
neither (a) nor (b).

A

both (a) and (b)

121
Q

What is the degree of freedom of an absorption process in which only one component is transferred between phases?
3
2
4
1

A

3

122
Q

Sticky material can be dried in a __________ dryer.
tray
rotary
fluidised bed
none of these

A

tray

123
Q

Langmuir equation is associated with
leaching
adsorption
steam distillation
multicomponent absorption.

A

adsorption

124
Q

During the constant rate period of drying of a solid,
increased air humidity decreases the rate of drying.
increasing the air temperature decreases the drying rate.
surface evaporation of unbound moisture occurs.
none of these.

A

surface evaporation of unbound moisture occurs.

125
Q

At a fixed total pressure, humidity depends only on the
partial pressure of vapour in the mixture.
heat capacity of the vapour.
density of the vapour.
none of these.

A

partial pressure of vapour in the mixture.

126
Q

If moisture content of solid on dry basis is X, then the same on wet basis is
X/X+1
X/1-X
1+X/X
1-X/X

A

X/X+1

127
Q

Flash distillation is
same as differential distillation.
used for multicomponent systems like crude refining.
same as simple distillation.
most useful for handling binary systems.

A

used for multicomponent systems like crude refining.

128
Q

__________ developed the film theory.
Higbie
Fick
Ergun
Levenspeil

A

Higbie

HF Higbie Film

129
Q

For absorbers, high pressure drop results in
increased efficiency.
decreased efficiency.
high operating cost.
better gas liquid contact.

A

high operating cost.

130
Q

Which of the following parameters remains almost constant during adiabatic saturation of unsaturated air?
Dry bulb temperature
Dew point
Wet bulb temperature
None of these

A

Wet bulb temperature

131
Q

Coffee is prepared from coffee beans by leaching with
cold water
hot water
dilute hot caustic solution
naphtha

A

hot water

132
Q

Gaseous diffusion co-efficient increases with increase in the
pressure
temperature
both (a) & (b)
neither (a) nor (b)

A

temperature

133
Q

With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature)
increases
remains unchanged
decreases
decreases linearly

A

increases

134
Q

Pick out the wrong statement. Raoult’s law does not apply, when the
size of component molecules are not equal.
attractive forces between like and unlike molecules in the solution are approximately equal.
component molecules are nonpolar.
chemical combination or molecular association between unlike molecules takes place in the formation of solution.

A

component molecules are nonpolar.

135
Q

Water-ethyl alcohal solution can be concentrated (in respect of alcohal concentration) by __________ distillation.
atmospheric
vacuum
high pressure
none of these

A

vacuum

136
Q

L/mG is the expression for
absorption factor
Brinkman number
slope of operating line in absorber
slope of operating line in stripper.

A

absorption factor

137
Q

Extraction of pencillin employs a __________ extraction coloumn.
centrifugal
packed
plate
None of these.

A

centrifugal

pencillin centrifugal

138
Q

In case of gases, the binary diffusivity is proportional to (where, P = pressure)
P
1/P
1/sqrt(P)
sqrt(P)

A

1/P

139
Q

When the gas to be dissolved in liquid is a/an __________ then normally co-current adsorber are used.
mixture of two gases
pure gas
ideal gas
sparingly soluble gas

A

pure gas

co-current pure gas

140
Q

Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the __________ number.
Schmidt
Sherwood
Peclet
Stanton

A

Schmidt

141
Q

If a two phase system is in physical equilibrium; then it means that, the
escaping tendency of each component from the liquid phase to the vapor phase is exactly equal to that from vapor phase to liquid phase.
temperature of the liquid phase is equal to that of the vapor phase.
total pressure throughout the liquid phase is equal to that throughout the vapor phase.
all (a), (b) and (c).

A

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

142
Q

McCabe-Thiele method of binary distillation does not assume that the
sensible heat changes are negligible compared with latent heat changes.
molar latent heats of all components are equal.
heat of mixing is negligible.
none of these

A

none of these

143
Q

(NSh/NRe.NSc) is termed in mass transfer operation as the
Stanton number
Peclet number
thermal diffusivity
momentum diffusivity

A

Stanton number

144
Q

The Hatta number is important in
multicomponent distillation.
binary distillation.
gas absorption without chemical reaction.
gas absorption with chemical reaction.

A

gas absorption with chemical reaction.

Hatta with chemical

145
Q

When a multistage tray tower uses a minimum reflux ratio, it implies
infinite trays and maximum reboiler heat load.
infinite trays and minimum reboiler heat load.
minimum trays and minimum reboiler heat load.
minimum trays and maximum reboiler heat load

A

infinite trays and minimum reboiler heat load.

146
Q

CO2 can be absorbed by
hot cupric oxide
heated charcoal
cold Ca(OH)2
alumina

A

heated charcoal

147
Q

For the same process conditions, the reflux ratio of an unlagged distillation column
decreases in winter
increases in winter
increases in summer
none of these

A

increases in winter

148
Q

An ideal tower packing should not
have low weight per unit volume.
have large surface area per unit volume.
have large free cross-section.
hold up large amount of liquid in the packing.

A

hold up large amount of liquid in the packing.

DAY 2 (23 decks)

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