Mass Transfer

141.During the constant rate period of drying of a solid,

  1. Increased air humidity decreases the rate of drying
  2. Increasing the air temperature decreases the drying rate
  3. Surface evaporation of unbound moisture occurs
  4. None of these

Correct answer: (C)
Surface evaporation of unbound moisture occurs

142.Entrainer used in Azeotropic distillation should

  1. Form a low boiling azeotrope with one of the constituents of the mixture
  2. Form a new azeotrope of low relative volatility with one of the constituents of the mixture
  3. Have high latent heat of vaporisation
  4. Have high viscosity to provide high tray efficiency

Correct answer: (A)
Form a low boiling azeotrope with one of the constituents of the mixture

143.Equilibrium moisture of a solid is equal to the total moisture minus free moisture. Which of the following substances will have maxi-mum equilibrium moisture?

  1. Anthracite coal
  2. Rag paper
  3. Bamboo
  4. Inorganic solids

Correct answer: (C)
Bamboo

144.Equilibrium-moisture curves of different solids

  1. Are different
  2. Are same
  3. Depend on the humidity of the gas
  4. None of these

Correct answer: (A)
Are different

145.Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the

  1. High evaporation losses of water
  2. High pressure drop of the gas
  3. Difficulty in its fabrication
  4. None of these

Correct answer: (B)
High pressure drop of the gas

146.Experimental determination of _________ is done by wetted wall column method.

  1. Diffusion co-efficient
  2. Mass transfer co-efficient
  3. NTU
  4. None of these

Correct answer: (B)
Mass transfer co-efficient

147.Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 × 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is:

  1. 5.6 × 10-4
  2. 8.5 × 10-4
  3. 5.6 × 10-3
  4. 8.5 × 10-3

Correct answer: (B)
8.5 × 10-4

148.Extraction of coffee from its seed is done by

  1. Liquid-liquid extraction
  2. Leaching
  3. Extractive distillation
  4. Steam distillation

Correct answer: (B)
Leaching

149.Extraction of penicillin employs a _________ extraction column.

  1. Centrifugal
  2. Packed
  3. Plate
  4. None of these

Correct answer: (A)
Centrifugal

150.Fenske equation determines the

  1. Maximum number of ideal plates
  2. Height of the distillation column
  3. Minimum number of theoretical plates
  4. Optimum reflux ratio

Correct answer: (C)
Minimum number of theoretical plates

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