chemical engineering mass transfer MCQs – Page 19

Practise multiple-choice questions from chemical engineering mass transfer for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering mass transfer Mcqs

361. In a counter-current liquid extractor___________________?
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A. Both liquids flow at fixed rate

B. Both liquids can have any desired flow rate

C. Only one of the liquids may be pumped at any desired rate

D. Liquids flow rate depends upon the temperature and pressure

362. Liquid diffusivity is of the order of _______________ cm2 /second?
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A. > 1

B. 10-5 to 10-6

C. 0.1

D. 0.01

363. Air initially at 101. 3 kPa and 40C and with a relative humidity of 50%, is cooled at constant pressure to 30C. The cooled air has a____________________?
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A. Higher wet bulb temperature

B. Higher relative humidity

C. Higher absolute (specific) humidity

D. Higher dew point

364. At what value of reflux ratio, number of theoretical plates in a distillation column is minimum ?
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A. < 1

B. ?

C. 0

D. 1

365. Back-trapping in a distillation column ?
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A. Increases tray efficiency

B. Is desirable, as it provides improved vapour-liquid contact

C. Reduces pressure drop

D. Decreases tray efficiency

366. In which of the following unit operations, the selectivity is an important parameter ?
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A. Solvent extraction

B. Absorption

C. None of these

D. Distillation

367. In distillation, overhead product contains ______________________?
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A. Any number of components

B. Two components

C. Only one component

D. Only saturated liquid

368. The suitable evaporator for concentration of foaming liquids is a ______________________ evaporator?
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A. Short tube

B. Vacuum

C. Long tube

D. Falling film

369. To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate) ____________________?
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A. Increase both G and S

B. Decrease both G and S

C. Increase S and decrease G

D. Increase G and decrease S

370. At __________________ reflux, theoretical number of plates in a distillation coloumn is calculated using Fenske-Underwood equation?
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A. Minimum

B. Operating

C. Maximum permissible

D. Total

371. In liquid-liquid extraction, the number of phases at plait point is __________________?
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A. 3

B. 1

C. 2

D. 4

372. Penetration model (theory) for mass transfer was enunciated by _____________________?
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A. Higbie

B. Kissinevskii

C. Toor and Marcello

D. Danckwerts

373. If f is defined as above, then which of the following applies to a feed at dew point ?
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A. 0 < f < 1

B. f 1

C. f = 1

374. Bollman extractor___________________?
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A. Is a static bed leaching equipment

B. Is used for extraction of oil from oilseed

C. Employs only counter-current extraction

D. Is a centrifugal extractor

375. In case of liquids, the binary diffusivity is proportional to (where, T = temperature) _____________________?
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A. 1/T

B. T

C. T2

D. ?T

376. Rotary dryers cannot handle _______________ materials ?
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A. Sticky

B. Dry

C. Granular

D. Free flowing

377. JD factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by___________________?
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A. None of these

B. Nsh = 2

C. Nst = 2

D. Nsc = 2

378. Absorption accompanied with chemical reaction is exemplified by the absorption of___________________?
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A. Benzol present in coke oven gas by wash oil

B. SO2 in alkaline solution

C. All A., B. and C.

D. Ammonia in water

379. Unit operation involved in the prilling of urea is_____________________?
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A. Evaporation

B. Drying

C. Crystallisation

D. Both B. and C.

380. Which of the following plays an important role in problems of simultaneous heat and mass transfer ?
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A. Sherwood number

B. Prandtl number

C. Lewis number

D. Schmidt number

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