chemical engineering mass transfer MCQs – Page 5

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 Review each marked answer and report any item that may be outdated or unclear.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

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

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