Chemical Engineering - Diffusion in a Quiescent Medium Questions - Set 39 - ObjectiveBooks

Chemical Engineering - Diffusion in a Quiescent Medium Questions - Set 39

Practice Test: Question Set - 39

1. What is the reflux ratio at total reflux?
    (A) Zero
    (B) Infinity
    (C) Unity
    (D) Data insufficient

2. The operating line for an absorber is curved, when plotted in terms of
    (A) Mole fractions
    (B) Mole ratios
    (C) Partial pressure
    (D) Mass fractions

3. Which of the following is the most suitable for extraction in a system having very low density difference?
    (A) Mixer-settler extractor
    (B) Centrifugal extractor
    (C) Pulsed extractor
    (D) Packed extraction tower

4. (NSh/NRe.NSc) is termed in mass transfer operation as the
    (A) Stanton number
    (B) Peclet number
    (C) Thermal diffusivity
    (D) Momentum diffusivity

5. In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase.
    (A) Gas
    (B) Liquid
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

6. Positive deviation from Raoult's law means a mixture whose total pressure is
    (A) Greater than that computed for ideality
    (B) Less than that computed for ideality
    (C) Less than the sum of the vapor pressure of the components
    (D) None of these

7. Flooding results in
    (A) High tray efficiency
    (B) Low tray efficiency
    (C) High gas velocity
    (D) Good contact between the fluids

8. At minimum reflux ratio for a given separation
    (A) Number of plates is zero
    (B) Number of plates is infinity
    (C) Minimum number of the theoretical plates is required
    (D) Separation is most efficient

9. An ideal tower packing should not
    (A) Have low weight per unit volume
    (B) Have large surface area per unit volume
    (C) Have large free cross-section
    (D) Hold up large amount of liquid in the packing

10. Diffusion in concentrated solutions differs from that in dilute solutions, because of the change in the __________ with the concentration of the solution.
    (A) Degree of ideality
    (B) Viscosity
    (C) Both 'a '& 'b'
    (D) Neither 'a' nor 'b'

11. Make up water is supplied during cooling tower operation to compensate for water losses due to
    (A) Evaporation
    (B) Blowdown
    (C) Entrainment
    (D) All (a), (b) & (c)

12. The dimension of diffusivity is same as that of the
    (A) Density
    (B) Molal concentration
    (C) Kinematic viscosity
    (D) Velocity head

13. As the reflux ratio in a distillation column is increased from the minimum, the
    (A) Slope of the operating line in stripping section decreases
    (B) Number of plates decreases very slowly first and then more and more rapidly
    (C) Total cost first decreases and then increases
    (D) Liquid flow increases while the vapor flow decreases for a system

14. Fenske-Underwood equation used for calculating the minimum number of theoretical plates in distillation column is valid for
    (A) Constant molal overflow
    (B) Total reflux
    (C) Constant relative volatility
    (D) All (a), (b) and (c)

15. Solvent used in extractive distillation
    (A) Is of low volatility
    (B) Forms a low boiling azeotrope
    (C) Forms a high boiling azeotrope
    (D) Does not alter the relative volatility of the original components

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