chemical engineering mass transfer MCQs – Page 3

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 Review each marked answer and report any item that may be outdated or unclear.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
41. Dorr thickener is an equipment used for___________________?
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A. Classification

B. Clarification

C. Sedimentation

D. Leaching

42. Mass transfer co-efficient is directly proportional to DAB according to the _____________ theory?
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A. Film

B. Penetration

C. None of these

D. Surface-renewal

43. Plate efficiency in a distillation column is reduced due to the ______________________ of liquid?
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A. Foaming

B. Entrainment

C. Weeping & dumping

D. All A., B. & C.
44. The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if___________________?
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A. NSc = NLe

B. NPr = NLe

C. NSc = NPr = NLe

D. NSc = 1

45. Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and t is time) ?
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A. (De.t)1/2

B. (4De/?t)1/2

C. (4De/t)

D. (De/t)1/2

46. Can the efficiency of a plate in the distillation tower be greater than 100% ?
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A. Never

B. Yes; if the reflux ratio is maximum

C. Yes

D. Normally not; but is possible if infinite number of plates are put

47. The boiling points of pure components of a binary system ________________ with increase in total pressure of the system ?
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A. May increase or decrease, depends on the system

B. Remains unchanged

C. Increases

D. Decreases

48. The operating cost of a distillation column at minimum reflux ratio is____________________?
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A. Infinite

B. Maximum

C. Zero

D. Minimum
49. To get high tray efficiency___________________?
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A. Time of contact between the two phases should be less

B. Liquid entrainment should be severe

C. Gas velocity should be very low

D. Interfacial surface between liquid and gas phase should be large
50. The humid volume may be increased by increasing the____________________?
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A. Temperature at constant humidity

B. Humidity at constant temperature

C. Both A. and B.

D. Neither A. nor B.

51. Blowdown in a cooling tower__________________?
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A. All A., B. & C.

B. Is undesirable

C. salt and impurities</strong>

D. Means discarding a small fraction of circulating water to prevent and limit the concentration

E. Increases the scale forming tendencies of water

52. The relative volatility of a binary mixture at the Azeotropic composition is _______________________?
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A. 1

B. 0

C. > 1

D. ?

53. Separation of two volatile liquids by distillation makes use of their___________________?
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A. Relative volatility

B. Solubility

C. Selectivity

D. Density difference

54. Ammonia present in the coke oven gas is removed by washing with___________________?
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A. Dilute ammoniacal liquor

B. Dilute HCl

C. Caustic solution

D. Ethanolamine

55. In extraction, as the temperature increases, the area of heterogeneity (area covered by binodal curve)____________________?
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A. Increases

B. None of these

C. Decreases

D. Remains unchanged

56. Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the _______________ moisture?
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A. Bound

B. Equilibrium

C. Unbound

D. Free

57. The dew point of an unsaturated gas-vapor mixture does not depend upon the ____________________ of the mixture?
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A. Temperature

B. All A., B. and C.

C. Total pressure

D. Composition

58. High pressure at the bottom of a distillation tower handling heat sensitive materials results in____________________?
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A. Increased relative volatility

B. Very efficient operation

C. Thermal decomposition of bottoms

D. Erosion of the tower

59. Blowdown in a cooling tower____________________?
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A. salt and impurities</strong>

B. Means discarding a small fraction of circulating water to prevent and limit the concentration

C. All A., B. & C.

D. Increases the scale forming tendencies of water

E. Is undesirable

60. In Azeotropic mixture, the equilibrium vapour composition is____________________?
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A. More than liquid composition

B. Less than liquid composition

C. Same as liquid composition

D. Independent of pressure