chemical engineering mass transfer Mcqs
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

61. The most efficient cooling tower out of the following is_____________________?
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A. Induced draft

B. Atmospheric

C. Forced draft

D. Natural draft

62. Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thieles method ?
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A. Partial condenser

B. Total condenser

C. Reboiler

D. Both B. and C
63. With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop___________________?
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A. Remains unchanged

B. Increases

C. Decreases exponentially

D. Decreases

64. Co-current absorbers are usually used when the gas to be dissolved in the liquid is ___________________?
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A. Highly soluble

B. Sparingly soluble

C. A pure substance

D. A mixture

65. Plate efficiency_______________________?
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A. Increases due to foaming

B. Increases due to weeping and dumping of liquid

C. Increases due to liquid entrainment

D. Is a function of the mass transfer between liquid and vapour
66. Which of the following parameters remains constant during chemical dehumidification ?
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A. Wet bulb temperature

B. None of these

C. Partial pressure of vapour

D. Dry bulb temperature
67. The slope of 9-line is determined by the__________________?
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A. Plate efficiency to be achieved

B. Relative volatility

C. Thermal condition of the feed

D. Reflux ratio

68. In McCabe-Thiele method, at infinite reflux ratio___________________?
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A. Number of plates is maximum

B. Overhead product is maximum

C. Both the operating lines coincide with the diagram

D. None of these

69. Molecular distillation is_____________________?
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A. High temperature distillation

B. For heat-sensitive materials

C. Very low pressure distillation

D. Both B. and C.
70. With increase in the mass velocity of the gas, the rate of drying during the constant rate period ______________, if the conduction and radiation through the solid are negligible ?
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A. Remain same

B. Increases linearly

C. Increases

D. Decreases

71. At 750K and 1 atm, the approximate value of Schmidt number for air is_________________?
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A. 0.01

B. 10

C. 0.1

D. 1

72. In gas-liquid contact operation, the number of ideal stages, N = (xa xb)/(xb x*b). This is true when the stripping factor S is ________________?
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A. S = 1

B. S > 1

C. S = ?

D. S < 1

73. Operating velocity in a packed tower is usually __________________ the flooding velocity ?
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A. Twice

B. More than

C. Equal to

D. Half
74. The Hatta number is important in______________________?
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A. Gas absorption without chemical reaction

B. Multi-component distillation

C. Binary distillation

D. Gas absorption with chemical reaction
75. The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is____________________?
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A. 0.5

B. 50

C. 2

D. 150

76. Which of the following increases during evaporative cooling process with recirculated water supply ?
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A. Wet bulb temperature

B. Relative humidity

C. Partial pressure of vapour

D. Both B. and C.
77. Pick out the wrong statement. Raoults law does not apply, when the______________________?
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A. mation of solution

B. Component molecules are non-polar

C. Chemical combination or molecular association between unlike molecules takes place in the

D. Size of component molecules are not equal

E. Attractive forces between like and unlike molecules in the solution are approximately equal

78. H2S present in naphtha reformed gas is removed by absorbing with___________________?
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A. HCl

B. Ethanolamine

C. K2CO3

D. Vacuum gas oil

79. Pick out the wrong statement ?
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A. Mechanical agitation is required, if the system has low interfacial tension

B. Sieve tray towers are generally used for systems having low interfacial tension

C. When Henrys law constant is very small, then the mass transfer rate is controlled by the gas

D. m resistance

E. Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar

F. turbulent layers

80. Drying of a solid involves _________________ transfer ?
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A. Only heat

B. Only mass

C. Both heat and mass

D. None of these

81. Pick out the wrong statement?
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A. According to Poiseuilles law, the permeability decreases with increase in temperature for

B. cess

C. Particles movement from higher concentration to lower concentration takes place in diffusion

D. The binary diffusivity in liquids is of the order of 10-5 cm2/sec

E. Molecular diffusion in solid is much faster than that in liquids

F. w of a gas through a given capillary

82. Lewis number (Le) is___________________?
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A. Pr St

B. Sc Pr

C. Sh Pr

D. St Sh

83. Unsaturated air (with dry and wet bulb temperatures being 35 and 25C respectively) is passed through water spray chamber maintained at 35C. The air will be__________________?
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A. Cooled

B. Humidified

C. Both A. & B.

D. Dehumidified

84. With the lowering of equilibrium pressure, at a given temperature, the amount of adsorbate on the adsorbent______________________?
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A. Decreases

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

C. Increases

D. Remain same

85. Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a _______________ column?
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A. Wetted wall

B. Packed

C. Bubble cap plate

D. Spray

86. A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)) ?
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A. MXo ln(Xo/XF)

B. M(Xo XF)

C. M(Xo/XF)

D. M ln(Xo/XF)

87. Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation ?
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A. Selectivity

B. Availability

C. Cost

D. Toxicity

88. pertaining to the analogy between equations of heat and mass transfer operations ?
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A. k out the wrong statement

89. Rayleighs equation applies to _________________ distillation?
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A. Continuous

B. Differential

C. Flash

D. Steam

90. The wet and dry bulb temperature for a vapour-gas mixture are 25C and 30C respectively. If the mixture is heated to 45C at constant pressure, the wet bulb temperature will be ______________ C ?
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A. 25

B. < 25

C. > 25

D. 25

91. Steam distillation is not recommended to be used, if the _____________________?
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A. Azeotropic mixture is to be separated and the final product is miscible with water

B. Material to be distilled is thermally unstable or has the tendency to react with other

C. Material cannot be distilled by indirect heating even under low pressure, because of the high

D. ponents associated with it, at the boiling temperature

E. ling temperature

F. Liquids decompose, if distilled directly at atmospheric pressure

92. Which one of the following devices is not used for both the absorption as well as the liquidliquid extraction processes ?
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A. Packed towers

B. Wetted wall columns

C. Plate towers

D. Spray towers

93. In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the ______________ number ?
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A. Grashoff

B. None of these

C. Sherwood

D. Lewis
94. Pick out the wrong statement pertaining to the analogy between equations of heat and mass_________________?
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A. nsfer operations.

B. Sherwood number in mass transfer is analogous to Nusselt number in heat transfer

C. Prandtl number in heat transfer is analogous to Schmidt number in mass transfer

D. Reynolds number in mass transfer is analogous to Grashoff number in heat transfer

E. Reynolds number remains the same in both heat and mass transfer

95. With increase in temperature, the leaching rate increases due to__________________?
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A. Decreased liquid viscosity

B. Increased diffusivity

C. Both A. and B.

D. Neither A. nor B.

96. The minimum liquid rate to be used in an absorber corresponds to an operating line_______________________?
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A. None of these

B. Tangential to the equilibrium curve

C. Of slope = 0.1

D. Of slope = 1

97. Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant____________________?
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A. Velocity

B. All A., B. & C.

C. Humidity

D. Temperature

98. For water-ethanol system, the minimum reflux ratio_____________________?
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A. Is computed from the intercept of the operating line

B. Is computed from the slope of the upper operating line that is tangent to the equilibrium curve

C. Is the optimum reflux ratio

D. Cannot be computed

99. Use of natural draft cooling tower is practised, when the air has low ?
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A. Humidity

B. Temperature

C. Both A. & B.

D. Neither A. nor B.

100. In liquid extraction, if the selectivity is unity, then__________________?
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A. Amount of solvent required will be minimum

B. Solvent flow rate should be very low

C. No separation will occur

D. Separation of the constituents is the most effective