Mass Transfer

181.For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around

  1. 0.6
  2. 0.24
  3. 1
  4. 0.72

Correct answer: (C)
1

182.For the flow of gases through a capillary, with increase in temperature, the permeability _________ as per Knudsen law.

  1. Increases
  2. Decreases
  3. Remain same
  4. Either (A) or (B); depends on the gas

Correct answer: (A)
Increases

183.For the gas absorption, the height of a transfer unit, based on the gas phase is given by (G: superficial molar gas velocity, L: superficial molar liquid velocity, FG: mass transfer co-efficient, moles/m2, a: interfacial area per unit volume of tower)

  1. G/(FG . a)
  2. FG/(G . a)
  3. (G . a)/FG
  4. L/(FG . G)

Correct answer: (A)
G/(FG . a)

184.For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will

  1. Increase
  2. Decrease
  3. Remain same
  4. Data insufficient, can't be predicted

Correct answer: (A)
Increase

185.For the same process conditions, the reflux ratio of an unlagged distillation column

  1. Decreases in winter
  2. Increases in winter
  3. Increases in summer
  4. None of these

Correct answer: (B)
Increases in winter

186.For the same system, if the same liquid used in an absorber is decreased, the tower height will

  1. Increase
  2. Decrease
  3. Remain unaffected
  4. Decrease or increase; depends on the type of liquid

Correct answer: (A)
Increase

187.For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as

  1. Re0.33
  2. Re0.53
  3. Re0.83
  4. Re

Correct answer: (C)
Re0.83

188.For water-ethanol system, the minimum reflux ratio

  1. Is computed from the slope of the upper operating line that is tangent to the equilibrium curve
  2. Is computed from the intercept of the operating line
  3. Cannot be computed
  4. Is the optimum reflux ratio

Correct answer: (A)
Is computed from the slope of the upper operating line that is tangent to the equilibrium curve

189.For which of the following unit operations, Lewis number is of significance?

  1. Adsorption
  2. Binary distillation
  3. Gas absorption
  4. Humidification

Correct answer: (D)
Humidification

190.Fractional solvent extraction

  1. Employs only one solvent
  2. Employs two solvents
  3. Results in low interfacial tension
  4. None of these

Correct answer: (B)
Employs two solvents

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