Mass Transfer MCQs

Question 1

Mass transfer co-efficient of liquid is

Accepted Answer

Affected more by temperature than that for gases

Answer

Affected much less by temperature than that for gases

Answer

Not affected by the temperature

Answer

None of these

Question 2

McCabe-Thiele method

Accepted Answer

Uses molal units for material and energy balance

Answer

Uses weight fractions to express liquid and vapour composition

Answer

Can use any type of units

Answer

Is more accurate than Ponchan-Savarit method

Question 3

In a moderately sized packed absorption tower, channeling (which is most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter

Accepted Answer

> 8:1

Answer

> 4 :1

Answer

< 8 : 1

Answer

< 6:1

Question 4

Flash distillation is suitable for separating the constituents of a binary system, which

Accepted Answer

Have very wide boiling points

Answer

Form minimum boiling azeotrope

Answer

Have very close boiling points

Answer

Form constant boiling azeotrope

Question 5

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

Accepted Answer

Increase

Answer

Decrease

Answer

Remains same

Answer

Depend on saturated boiling point; may increase or decrease

Question 6

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is

Accepted Answer

1.24

Answer

0.54

Answer

1.04

Answer

1.94

Question 7

The surface renewal frequency in Danckwerts model of mass transfer is given by (K L : mass transfer co-efficient)

Accepted Answer

$$\sqrt {{{	ext{K}}_{	ext{L}}}^2 \cdot {{	ext{D}}_{	ext{A}}}} $$

Answer

$${{	ext{K}}_{	ext{L}}}^2 \cdot {{	ext{D}}_{	ext{A}}}$$

Answer

$$\frac{{{{	ext{K}}_{	ext{L}}}^2}}{{{{	ext{D}}_{	ext{A}}}}}$$

Answer

$$\frac{{{{	ext{K}}_{	ext{L}}}}}{{{{	ext{D}}_{	ext{A}}}^2}}$$

Question 8

In a packed tower, the value of HETP equals HTU OG , when the equilibrium and the operating lines are (where, HETP = height equivalant to a theoretical plate HTU OG = overall gas phase height of a transfer unit)

Accepted Answer

Both A & B

Answer

Straight

Answer

Parallel

Answer

Neither A nor B

Question 9

Priming in a distillation column

Accepted Answer

Is characterised by the presence of foam throughout the space between trays

Answer

Results from very low gas velocity

Answer

Is desirable from point efficiency consideration

Answer

Reduces the overall pressure drop