INDIABIX-MASS TRANSFER

Question 1

Fenske equation determines the

maximum number of ideal plates.
height of the distillation column.
minimum number of theoretical plates.
optimum reflux ratio.

Answer 1

minimum number of theoretical plates.

Question 2

The term “cooling range” in a cooling tower refers to the difference in the temperature of

A) cold water leaving the tower and the wet bulb temperature of the surrounding air.
B) hot water entering the tower and the wet bulb temperature of the surrounding air.
C) hot water entering the tower and the cooled water leaving the tower.
D) none of these

Answer 2

C) hot water entering the tower and the cooled water leaving the tower.

Question 3

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

Answer 3

Centrifugal extractor

Question 4

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

Answer 4

Centrifugal extractor

Question 5

Total reflux in a distillation operation requires minimum

reboiler load
number of plates
condenser load
all (a), (b) and (c)

Answer 5

number of plates

Question 6

The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is

+ve
-ve
zero
none of these

Answer 6

+ve

Question 7

Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the

A) relative volatility is reasonably constant.
B) mixture (to be separated) shows negative deviation from ideality.
C) mixture (to be separated) shows positive deviation from ideality.
D) multicomponent distillation is involved.

Answer 7

A) relative volatility is reasonably constant.

Question 8

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

natural
forced
induced
none of these

Answer 8

natural

Question 9

__________ columns are used for liquid dispersion in a continuous gas phase.

Packed
Pulse
Bubble cap
Sieve plate

Answer 9

Packed

Question 10

Overall efficiency of the distillation column is

the ratio of number of ideal plates to actual plates.
the ratio of number of actual plates to ideal plates.
same as the Murphree efficiency.
always more than the point efficiency.

Answer 10

the ratio of number of ideal plates to actual plates.

Question 11

Drying operation under vacuum is carried out to

A) dry those materials which have very high unbound mositure content.
B) reduce drying temperature.
C) increase drying temperature.
D) dry materials having high bound moisture content.

Answer 11

B) reduce drying temperature.

Question 12

Separation of two or more components of a liquid solution can not be achieved by

fractional crystallisation
liquid extraction
absorption
evaporation

Answer 12

absorption

Question 13

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.

Answer 13

number of plates is infinity.

Question 14

Relative humidity is the ratio of the

A) partial pressure of the vapour to the vapour pressure of the liquid at room temperature.
B) partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
C) actual humidity to saturation humidity.
D) none of these

Answer 14

B) partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.

Question 15

In batch distillation with constant reflux, overhead product composition __________ with time.

increases
decreases
does not vary
may increase on decrease, depends on the system.

Answer 15

decreases

Question 16

Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the __________ of a fibre.

electrical resistance
thermal conductivity
strength
none of these.

Answer 16

electrical resistance

Question 17

Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the

latent heat
humid heat
specific heat
sensible heat

Answer 17

specific heat

Question 18

Dew point of a gas-vapour mixture

increases with temperature rise.
decreases with temperature rise.
decreases with decrease in pressure.
increases with increase in pressure.

Answer 18

decreases with decrease in pressure.

Question 19

Which of the following plays an important role in problems of simultaneous heat and mass transfer?

Lewis number
Schmidt number
Prandtl number
Sherwood number

Answer 19

Lewis number

Question 20

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.

Answer 20

line always lies above the equilibrium curve.

Question 21

As the reflux ratio in a distillation coloumn is increased from the minimum, the

A) slope of the operating line in stripping section decreases.
B) number of plates decreases very slowly first and then more and more rapidly.
C) total cost first decreases and then increases.
D) liquid flow increases while the vapor flow decreases for a system.

Answer 21

C) total cost first decreases and then increases.

Question 22

A plait point is the point on the solubility curve, where the tie line reduces to a point. What is the number of plait point for a ternery system containing twopairs of partially miscible liquids ?

0
1
2
3

Answer 22

0

Question 23

Which of the following unit operations makes use of Thiele-Geddes equation ?

Liquid-liquid extraction
Solid-liquid extraction
Multicomponent absorption with chemical reaction
Multicomponent distillation.

Answer 23

Multicomponent distillation.

Question 24

Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty ?

Sieve plate column
Bubble cap column
Randomly packed column
Wetted wall column

Answer 24

Wetted wall column

Question 25

The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is

natural draft cooling tower
induced draft cooling tower
spray chamber
none of these

Answer 25

spray chamber

Question 26

Chemisorption (chemical adsorption) is

same as “Van der Waals” adsorption.
characterised by adsorption of heat.
an irreversible phenomenon.
a reversible phenomenon.

Answer 26

an irreversible phenomenon.

Question 27

Raoult’s law applies to the

all liquid solutions
non-ideal solution only.
non-volatile solute.
solvents.

Answer 27

solvents.

Question 28

In distillation columns, the number of bubble caps per tray primarily depends upon the

allowable liquid velocity.
allowable gas velocity.
allowable gas and liquid velocities.
feed composition.

Answer 28

allowable gas and liquid velocities.

Question 29

In distillation, overhead product contains

only one component
two components
any number of components
only saturated liquid

Answer 29

any number of components

Question 30

With increase in pressure, the relative volatility for a binary system

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

Answer 30

decreases.