Mass Transfer MCQs

Question 1

Pick out the wrong statement:

Accepted Answer

The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity

Answer

Change in barometric pressure does not affect the relative humidity

Answer

In case of a packed tower, the operating velocity is about half of the flooding velocity, generally

Answer

'Elution' means the desorption of the adsorbed solute by a solvent

Question 2

A 25 cm × 25 cm × 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1 m × 1 m × 1 cm flat sheet of the same material is to be dried from one side only. Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is

Accepted Answer

1000

Answer

1500

Answer

2000

Answer

2500

Question 3

Relative volatility varies with the concentration of component for an ideal solution. The relative volatity of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when

Accepted Answer

Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law

Answer

Only vapor phase follows Raoult's law

Answer

Only liquid phase obeys Dalton's law

Answer

Liquid phase obeys Dalton's law and vapor phase obeys Raoult's law

Question 4

Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.

Accepted Answer

Wetted wall

Answer

Bubble cap

Answer

Perforated tray

Answer

Packed

Question 5

The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid )

Accepted Answer

T

Answer

$$\sqrt {	ext{T}} $$

Answer

T 1.5

Answer

T 3

Question 6

At minimum reflux ratio for a given separation

Accepted Answer

Number of plates is infinity

Answer

Number of plates is zero

Answer

Minimum number of the theoretical plates is required

Answer

Separation is most efficient

Question 7

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

Accepted Answer

Hot water entering the tower and the cooled water leaving the tower

Answer

Cold water leaving the tower and the wet bulb temperature of the surrounding air

Answer

Hot water entering the tower and the wet bulb temperature of the surrounding air

Answer

None of these

Question 8

Pick out the wrong statement.

Accepted Answer

Mechanical agitation is required, if the system has low interfacial tension

Answer

Seive tray towers are generally used for systems having low interfacial tension

Answer

When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance

Answer

Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar and turbulent layers

Question 9

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

Accepted Answer

Both B and C

Answer

Wet bulb temperature

Answer

Relative humidity

Answer

Partial pressure of vapour