chemical engineering mass transfer MCQs – Page 22

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 Review each marked answer and report any item that may be outdated or unclear.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

421. A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state ?
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A. Composition of vapors and that of liquid do not vary throughout the column

B. The top and bottom compositions correspond to the maximum enrichment available

C. The top and bottom compositions are unchanged with and without total reflux

D. Reboiler load and condenser load are minimum

422. Azeotropism for ethyl alcohol-water system disappears by_____________________?
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A. Decreasing pressure

B. Increasing pressure

C. No means

D. Increasing temperature

423. Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the ________________ of a fibre ?
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A. None of these

B. Thermal conductivity

C. Electrical resistance

D. Strength

424. For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will_____________________?
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A. Data insufficient, cant be predicted

B. Remain same

C. Decrease

D. Increase

425. Schmidt number and Lewis number for pure air at atmospheric conditions are respectively__________________?
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A. > 1 and ? 1

B. < 1 and ? 1

C. 0 and ? 1

D. 1 and 0

426. Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if____________________?
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A. There is equimolar counter diffusion

B. Mass transfer is accompanied by reaction

C. Diffusion of A is in stagnant medium B

D. Molecular mean free path is high

427. The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is___________________?
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A. +ve

B. None of these

C. Zero

D. #NAME?

428. With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas________________?
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A. Increases

B. Decreases linearly

C. Remain unaffected

D. Decreases

429. In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of_______________________?
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A. None of these

B. Condenser and reboiler surfaces

C. Area between operating line and 45 diagonal x-y diagram

D. Tower cross-section

430. In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________________ its relative saturation?
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A. Higher than

B. Either A. or B., depends on the mixture composition

C. Equal to

D. Lower than

431. Calcium ammonium nitrate (a fertiliser) is dried in a _________________ dryer?
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A. Tunnel

B. Vacuum

C. Tray

D. Rotary

432. Mass transfer co-efficient (K) and diffusivity D. are related according to film theory as______________________?
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A. K ??D

B. K ? D

C. K ? D1.5

D. K ? D2

433. Moisture contained by a substance in excess of the equilibrium moisture is called the _______________ moisture?
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A. Free

B. Bound

C. Unbound

D. Critical

434. For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around____________________?
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A. 1

B. 0.6

C. 0.24

D. 0.72

435. With increase in temperature, the solubility of gases in liquids, at fixed pressure____________________?
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A. Remain same

B. Decreases

C. Increases

D. Either A. or B., depends on the system

436. The term approach in a cooling tower refers to the difference in the temperature of the____________________?
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A. Hot water entering and the cooled water leaving the cooling tower

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

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

D. None of these

437. Molecular sieves are porous____________________?
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A. Silica

B. Alumina

C. None of these

D. Synthetic zeolites crystals/metal alumino-silicates

438. Rose oil is extracted from rose leaves using ____________ distillation?
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A. Steam

B. High pressure

C. Low pressure

D. Extractive

439. Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (yin = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is, N+2 = 6 log (yin/yout).For 98% recovery of acetone, the number of trays required is/are ?
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A. 4

B. 8

C. 9

D. 10

440. Small dia distillation column can be a _________________________?
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A. Bubble cap

B. Any of these

C. Sieve tray

D. Packed column

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