Mass Transfer MCQs

Question 1

Pick out the wrong statement.

Accepted Answer

For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 × 10 -2 m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2 m/s

Answer

In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed

Answer

In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency

Answer

The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Question 2

In steam distillation, the

Accepted Answer

Product must be immiscible with water

Answer

Temperature is 100°C

Answer

Temperature is more than 100° C

Answer

Temperature is higher than the boiling point of either component

Question 3

The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.

Accepted Answer

Exponential

Answer

Parabolic

Answer

Linear

Answer

Cubic

Question 4

The adiabatic saturation curve for a vapour-gas mixture is

Accepted Answer

Slightly concave upward

Answer

Straight line

Answer

Slightly concave downward

Answer

None of these

Question 5

The falling rate period in the drying of a solid is characterised by

Accepted Answer

Increasing temperatures both on the surface and within the solid

Answer

Increase in rate of drying

Answer

Decreasing temperatures

Answer

None of these

Question 6

Solvent used in extractive distillation

Accepted Answer

Changes the relative volatility of the original components

Answer

Should be of high volatility

Answer

Should form azeotropes with the original components

Answer

All of the above

Question 7

With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system)

Accepted Answer

Increases

Answer

Decreases

Answer

Remains unaffected

Answer

Increases Linearly

Question 8

As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches

Accepted Answer

That of normal condensation

Answer

Integral heat of adsorption

Answer

Zero

Answer

None of these

Question 9

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?

Accepted Answer

The mixture exhibits an azeotrope at 101.3 kPa

Answer

The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10

Answer

The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10

Answer

The mixture contain optical isomers