Mass Transfer MCQs

Question 1

Stefan's law describes the mass transfer by

Accepted Answer

Both A & B

Answer

Diffusion

Answer

Bulk flow

Answer

Neither A nor B

Question 2

Liquid diffusivity is of the order of __________ cm 2 /second.

Accepted Answer

10 -5 to 10 -6

Answer

0.01

Answer

0.1

Answer

> 1

Question 3

Pick out the wrong statement.

Accepted Answer

Relative volatility of a binary mixture changes appreciably with the minor change in temperature

Answer

Constant pressure distillation can not separate an azeotropic mixture

Answer

The relative volatility of a binary mixture at azeotropic composition is unity

Answer

Flash distillation is practised on wide spread scale in petroleum refinery

Question 4

As per Gilliland's equation, the diffusivity is

Accepted Answer

All of the above

Answer

Directly proportional to 'T 1.5 '

Answer

Inversely proportional to 'P'

Answer

Dependent on the molecular volume & molecular weight of components

Question 5

Milk is dried usually in a __________ dryer.

Accepted Answer

Spray

Answer

Freeze

Answer

Tray

Answer

Rotary

Question 6

Pick out the wrong statement.

Accepted Answer

Diameter of randomly packed tower is normally more than 1.2 metres

Answer

Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the possibility of tower wall collapse

Answer

Packed towers are preferred over plate towers for handling corrosive and foamy liquids

Answer

Due to uneven supply and improper distribution of liquid, problem of channeling, loading & flooding is generally encountered in packed towers

Question 7

The dimension of diffusivity is same as that of the

Accepted Answer

Kinematic viscosity

Answer

Density

Answer

Molal concentration

Answer

Velocity head

Question 8

Back-trapping in a distillation column

Accepted Answer

Decreases tray efficiency

Answer

Increases tray efficiency

Answer

Reduces pressure drop

Answer

Is desirable, as it provides improved vapour-liquid contact

Question 9

Which of the following decreases during evaporative cooling process with recirculated water supply?

Accepted Answer

None of these

Answer

Wet bulb temperature

Answer

Relative humidity

Answer

Partial pressure of vapour