Questions and answers for exam Preparation

MCQs

Total Questions : 3241 | Page 2 of 325 pages

Question 11. In distillation columns, the number of bubble caps per tray primarily depends upon the

Allowable liquid velocity
Allowable gas velocity
Allowable gas and liquid velocities
Feed composition

Discuss Question

Answer: Option C. -> Allowable gas and liquid velocities

Question 12. Gaseous diffusivity at atmospheric pressure is of the order of __________ cm²/second.

1
1 to 5
5 to 10
> 10

Discuss Question

Answer: Option A. -> 1

Question 13. According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity)

D
D2
D0.5
1/D

Discuss Question

Answer: Option A. -> D

Question 14. For gas absorption, low viscosity solvents are preferred, because of their

Better flow characteristics
Low pumping pressure drop
Rapid absorption rates
All of the above

Discuss Question

Answer: Option D. -> All of the above

Question 15. The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the

Differential heat of adsorption
Heat of wetting
Integral heat of adsorption
None of these

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Answer: Option A. -> Differential heat of adsorption

Question 16. Pick out the wrong statement:

Change in barometric pressure does not affect the relative humidity
In case of a packed tower, the operating velocity is about half of the flooding velocity, generally
'Elution' means the desorption of the adsorbed solute by a solvent
The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity

Discuss Question

Answer: Option D. -> The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity

Question 17. On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in

Greater degree of separation with a fixed number of trays
Increased reboiler load
Increased reflux ratio
None of these

Discuss Question

Answer: Option C. -> Increased reflux ratio

Question 18. Steam distillation is not recommended to be used, if the

Azeotropic mixture is to be separated and the final product is miscible with water
Liquids decompose, if distilled directly at atmospheric pressure
Material can not be distilled by indirect heating even under low pressure, because of the high boiling temperature
Material to be distilled is thermally unstable or has the tendency to react with other components associated with it, at the boiling temperature

Discuss Question

Answer: Option A. -> Azeotropic mixture is to be separated and the final product is miscible with water

Question 19. Chemisorption compared to physical absorption has

Lower adsorption rate
Lower capacity of the solvent for the solute gas
Increased utilisation of stagnant zones of the liquid phase
None of these

Discuss Question

Answer: Option C. -> Increased utilisation of stagnant zones of the liquid phase

Question 20. At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent.