Mass Transfer

211.If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement.

  1. a1 = a2
  2. a1 = 2a2
  3. a1 = 0.5 a2
  4. None of these

Correct answer: (D)
None of these

212.If f = moles of vapour present per mole of feed, then the slope of feed line is (McCabe-Thiele method)

  1. (1 - ƒ)/ƒ
  2. - (ƒ - 1)/ƒ
  3. -1/ƒ
  4. -ƒ/(1 - ƒ)

Correct answer: (C)
-1/ƒ

213.If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is

  1. L/G
  2. G/L
  3. Always < 1
  4. None of these

Correct answer: (A)
L/G

214.If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is

  1. 0
  2. 1
  3. < 1
  4. > 1

Correct answer: (B)
1

215.If moisture content of solid on dry basis is X, then the same on wet basis is

  1. X/(X + 1)
  2. X/(1 - X)
  3. (1 + X)/X
  4. (1 - X)/X

Correct answer: (A)
X/(X + 1)

216.If Rm is the minimum reflux ratio, the optimum reflux ratio may be around _________ Rm.

  1. 1.2 to 1.5
  2. 2.5 to 3
  3. 3 to 4
  4. 5

Correct answer: (A)
1.2 to 1.5

217.If the amount of the steam used in steam distillation is increased, the temperature of distillation

  1. Increases
  2. Decreases
  3. Remains unchanged
  4. Depends on relative volatility

Correct answer: (B)
Decreases

218.If the overall efficiency and Murphree plate efficiency are equal, then both the equilibrium and operating lines are:

  1. Straight
  2. Parallel
  3. Both (A) & (B)
  4. Neither (A) nor (B)

Correct answer: (C)
Both (A) & (B)

219.If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be _________ percent.

  1. 100
  2. > 100
  3. < 100
  4. None of these

Correct answer: (B)
> 100

220.If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that

  1. The system comprises of partially miscible liquids
  2. The system comprises of miscible liquids
  3. The system comprises of an azeotrope
  4. On heating, a vapor phase will appear; while on cooling, a solid phase will appear

Correct answer: (D)
On heating, a vapor phase will appear; while on cooling, a solid phase will appear

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