Mass Transfer Set 10 MCQs

Q1 | Free flowing granular materials can be best dried in a __________ drier.

Rotary

Cylinder

Drum

Freeze

Q2 | In a packed bed absorption column, the channelling will be noted by the

Increase in flow rate

Sharp drop in pressure drop

Sharp rise in pressure drop

None of these

Q3 | The ratio of Murphree plate efficiency to point efficiency is always > 1 in a __________ flow model.

Plug

Perfectly mixed

Both (A) & (B)

Neither (A) nor (B)

Q4 | Fractional solvent extraction

Employs only one solvent

Employs two solvents

Results in low interfacial tension

None of these

Q5 | At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid__________ that in dry packed tower.

Is greater than

Is lower than

Is same as

Cannot be predicted as data are insufficient

Q6 | During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant.

Wet bulb temperature

Partial pressure of water vapor

Relative humidity

None of these

Q7 | Wet bulb and dry bulb temperatures becomes identical at __________ percent saturationcurve.

100

50

78

None of these

Q8 | __________ is the separation technique used for desalination of sea water.

Thermal diffusion

Reverse osmosis

Adsorption

Absorption

Q9 | The partial pressure distribution of an ideal gas diffusing through another stagnant idealgas at steady state follows a/an __________ law.

Exponential

Parabolic

Linear

Cubic

Q10 | Out of two equilibrium curves, first one lies above the diagonal and the second lies below the diagonal in the x-y plot. It means that separation by distillation is

Not possible in the second case unless vacuum is applied

Not possible in the second case unless high pressure is applied

More readily done in the second case compared to first one

None of these

Q11 | According to Chilton-Colburn analogy for mass transfer, NSt.NSc 2/3 is equal to

f

f/2

2f

1/f

Q12 | Very tall packed towers are divided into series of beds to

Reduce the overall pressure drop

Avoid channelling

Reduce liquid hold-up

Avoid flooding

Q13 | If „f’ is defined as above, then which of the following applies to a feed at dew point?

f = 1

f < 1

f > 1

0 < f < 1

Q14 | Separation of the isotopes of helium for scientific investigations is done by

Reverse osmosis

Thermal diffusion

Leaching

Solvent extraction

Q15 | Flash distillation is suitable for the separation of components

Having very close boiling points

Which form maximum boiling azeotrope

Having very wide boiling points

Which form minimum boiling azeotrope

Q16 | The McCabe ?L law states that the

Molar heats of vaporisation of components are nearly equal

Linear crystal growth rate depends on the degree of super-saturation

Linear crystal growth rate does not depend on the crystal size

Linear crystal growth rate depends on the crystal size

Q17 | When both the fluids flow concurrently in an absorber, the slope of the operating line is

#NAME?

1

-1

Q18 | Steam distillation is used for separation of high boiling

Substances from non-volatile impurities

Volatile impurity from still higher boiling substances

Both (A) and (B)

Neither (A) nor (B)

Q19 | The relative saturation of a partially saturated mixture of vapour and gas can be increasedby __________ of the mixture.

Reducing the total pressure

Increasing the total pressure

Reducing the temperature

Both (B) and (C)

Q20 | Pick out the correct statement.

Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation

A sharp decrease in pressure drop is an indication of flooding in a distillation coloumn

Solvent used in extractive distillation should be of high volatility

Flash distillation is suitable for separating components which have very close boiling temperature

Q21 | Pick out the wrong statement.

Constant pressure distillation cannot separate an Azeotropic mixture

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

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

Flash distillation is practised on wide spread scale in petroleum refinery

Q22 | For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams

Increases

Decreases

Remain unaffected

Passes through a maximum

Q23 | __________ diffusion is used for separating the isotopes of methane.

Thermal

Pressure

Concentration

Force

Q24 | Pick out the wrong statement.

The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one

Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference

According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2

The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Q25 | For a distillation column operating at minimum reflux, the

Concentration of liquid and vapour leaving a plate will be same

Reflux ratio will be maximum

Number of plates required will be maximum

None of these