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Philippine Chemical Engineering Licensure Examination Day 2 Separation Processes > IndiaBIX Chemical Engineering: Mass Transfer Section 10 > Flashcards

IndiaBIX Chemical Engineering: Mass Transfer Section 10 Flashcards

1
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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2
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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3
Q

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

A

steam

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4
Q

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

A

moving bed adsorption

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5
Q

Which of the following is the correct ternery diagram for liquid-liquid extraction system comprising of two pairs partly soluble (e.g., chlorobenzene-water-methyl ethyl ketone system) ?

A

0

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6
Q

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

A

leaching.

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7
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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8
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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9
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.

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10
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

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11
Q

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

A

more than

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12
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

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13
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.

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14
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

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15
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

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16
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

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17
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

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18
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.

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19
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.

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20
Q

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

A

elution

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21
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)

22
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.

23
Q

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

A

liquid extraction

24
Q

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

A

both (b) and (c)

25
Q

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

A

synthetic zeolites crystals/metal alumino-silicates.

26
Q

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

A

rotary

27
Q

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

A

extractive distillation

28
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.

29
Q

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

A

distillation column

30
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’.

31
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

32
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).

33
Q

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

A

long tube

34
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

35
Q

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

A

leaching

36
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

37
Q

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

A

> 1

38
Q

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

A

> 1

39
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.

40
Q

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

A

100

41
Q

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

A

Lewis number

42
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.

43
Q

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

A

Toor and Marchello

44
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

45
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.

46
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.

47
Q

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

A

crystallisation.

48
Q

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

A

fluid-solid

49
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

50
Q

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

A

thermal diffusion

Philippine Chemical Engineering Licensure Examination Day 2 Separation Processes (14 decks)

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