Mass Transfer

41.Absorption factor method is used to calculate the number of ideal stages, when

  1. Operating line lies above the equilibrium line
  2. Operating line lies below the equilibrium line
  3. Both operating and equilibrium lines are parallel
  4. Pressure drop in the column is very high

Correct answer: (C)
Both operating and equilibrium lines are parallel

42.Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be

  1. 1
  2. > 1
  3. < 1
  4. ≤ 1

Correct answer: (B)
> 1

43.According to Chilton-Colburn analogy for mass transfer, NSt.NSc 2/3 is equal to

  1. ƒ
  2. ƒ/2
  3. 2ƒ
  4. 1/ƒ

Correct answer: (B)
ƒ/2

44.According to Poiseuille's law, the permeability for gas flow through a capillary is proportional to (where, µ = gas viscosity)

  1. µ
  2. 1/µ
  3. õ
  4. µ2

Correct answer: (B)
1/µ

45.According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B? Assume that relative volatility (αAB = 2) does not change appreciably in the column.

  1. 5
  2. 9
  3. 12
  4. 28

Correct answer: (C)
12

46.According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity).

  1. D
  2. D2
  3. D0.5
  4. 1/D

Correct answer: (A)
D

47.Acetic acid will be most economically separated from a dilute solution of acetic acid in water by

  1. Solvent extraction
  2. Continuous distillation
  3. Evaporation
  4. Absorption

Correct answer: (A)
Solvent extraction

48.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:

  1. 4
  2. 8
  3. 9
  4. 10

Correct answer: (C)
9

49.Adsorption is a unit operation which generally involves _________ systems.

  1. Liquid-solid
  2. Gas-solid
  3. Fluid-solid
  4. Solid-solid

Correct answer: (C)
Fluid-solid

50.Advantage of continuous drying over batch drying is that the

  1. Drying cost per unit weight of dried product is less
  2. Product with more uniform moisture content is produced
  3. Equipment size required is smaller
  4. All 'a', 'b' & 'c'

Correct answer: (D)
All 'a', 'b' & 'c'

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