Mass Transfer

231.In a liquid-liquid extraction, 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X, where Y* is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer.

  1. The entire amount of C is transferred to solvent B
  2. Less than 2 kg but more than 1 kg of C is transferred to solvent B
  3. Less than 1 kg of C is transferred to B
  4. No amount of C is transferred to B

Correct answer: (A)
The entire amount of C is transferred to solvent B

232.In a moderately sized packed absorption tower, channelling (which is most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter

  1. > 4 :1
  2. < 8 : 1
  3. > 8:1
  4. < 6:1

Correct answer: (C)
> 8:1

233.In a packed absorption tower, if the equilibrium and operating lines are both straight lines, then the ratio, HETP/HTUOG _________ the absorption factor.

  1. Increases with increase in
  2. Is one at unity value of
  3. Both (A) and (B)
  4. Neither (A) nor (B)

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

234.In a packed bed absorption column, the channelling will be noted by the

  1. Increase in flow rate
  2. Sharp drop in pressure drop
  3. Sharp rise in pressure drop
  4. None of these

Correct answer: (B)
Sharp drop in pressure drop

235.In a packed tower, the value of HETP equals HTUOG, when the equilibrium and the operating lines are (where, HETP = height equivalent to a theoretical plate HTUOG = overall gas phase height of a transfer unit).

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

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

236.In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raffinate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg)

  1. 6.89
  2. 8.89
  3. 10
  4. 8.25

Correct answer: (B)
8.89

237.In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is

  1. 0.5
  2. 0.6
  3. 1
  4. 2

Correct answer: (A)
0.5

238.In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as

  1. KG = 1/KG + m/KL
  2. 1/KG = 1/KG + m/KL
  3. 1/KG = 1/KL + m/KG
  4. KG = 1/KL + m/KG

Correct answer: (A)
1/KG = 1/KG + m/KL

239.In an absorber, HETP does not vary with the

  1. Flow rate of liquid
  2. Flow rate of gas
  3. Type and size of packing
  4. None of these

Correct answer: (D)
None of these

240.In an absorption column, the flooding velocity for random packing is _________ that for stacked/regular packing.

  1. Greater than
  2. Smaller than
  3. Equal to
  4. Either (A), or (B); depends on the type of packing

Correct answer: (B)
Smaller than

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