Mass Transfer

491.The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is

  1. 2
  2. 0.5
  3. 50
  4. 150

Correct answer: (A)
2

492.The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp= M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.)

  1. Kc = Kp = Km
  2. Kc = Kp/RT = Km . RT/P
  3. Kc = Kp . RT = Km . RT/p
  4. None of these

Correct answer: (C)
Kc = Kp . RT = Km . RT/p

493.The relation, Sc = Pr = 1, is valid, when the mechanism of _________ transfer is same.

  1. Heat and mass
  2. Mass and momentum
  3. Heat and momentum
  4. Heat, momentum and mass

Correct answer: (A)
Heat and mass

494.The relative humidity of air decreases in-spite of an increase in the absolute humidity, when the

  1. Temperature rises
  2. Pressure rises
  3. Temperature falls
  4. Pressure falls

Correct answer: (A)
Temperature rises

495.The relative saturation of a partially saturated mixture of vapour and gas can be increased by _________ of the mixture.

  1. Reducing the total pressure
  2. Increasing the total pressure
  3. Reducing the temperature
  4. Both (B) and (C)

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

496.The relative saturation of an unsaturated mixture of gas and vapor is independent of the

  1. Nature of the vapor
  2. Temperature of the mixture
  3. Composition of the mixture
  4. None of these

Correct answer: (D)
None of these

497.The relative volatility of a binary mixture at constant temperature _________ the total pressure.

  1. Decreases with increase in
  2. Increases with increase in
  3. Is independent of
  4. None of these

Correct answer: (A)
Decreases with increase in

498.The relative volatility of a binary mixture at the Azeotropic composition is

  1. 1
  2. > 1
  3. 0
  4. ∞

Correct answer: (A)
1

499.The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc) for the same system is.

  1. 100
  2. 10
  3. 5
  4. 1

Correct answer: (B)
10

500.The rough value of diffusion co-efficient of water vapor into air at 25°C may be about _________ cm2/sec.

  1. 0.25
  2. 2.5
  3. 1.25
  4. 0.0025

Correct answer: (A)
0.25

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