What Causes Mass Transfer MCQ Practice Test - Set 43 - ObjectiveBooks

# Practice Test: Question Set - 43

1. At equilibrium the concentration of water in vapor phase (C*) in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapor initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is
(A) 0.0
(B) 0.2
(C) 0.4
(D) 1.0

2. In case of absorption with exothermic reaction, for fluids having
(A) Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence
(B) Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same
(C) Both (a) and (b)
(D) Pr = Sc; there won't be any change in heat and mass transfer flux with changes in degree of turbulence

3. Drying operation under vacuum is carried out to
(A) Dry those materials which have very high unbound moisture content
(B) Reduce drying temperature
(C) Increase drying temperature
(D) Dry materials having high bound moisture content

4. Sticky material can be dried in a __________ dryer.
(A) Tray
(B) Rotary
(C) Fluidized bed
(D) None of these

5. The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid).
(A) T
(B) T
(C) T1.5
(D) T3

6. The minimum number of theoretical plates is required for achieving a given separation in distillation column with
(A) No reflux
(B) Total reflux
(C) Zero reflux ratio
(D) Minimum reflux ratio

7. For which of the following unit operations, Lewis number is of significance?
(B) Binary distillation
(C) Gas absorption
(D) Humidification

8. Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapor by 1°F is called the
(A) Latent heat
(B) Humid heat
(C) Specific heat
(D) Sensible heat

9. With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature).
(A) Increases
(B) Remains unchanged
(C) Decreases
(D) Decreases linearly

10. As the reflux ratio decreases, the
(A) Separation becomes more efficient
(B) Number of plates increases
(C) Column diameter increases
(D) None of these

11. Only small amount of evaporation of water produces large cooling effects because of its
(A) Large latent heat
(B) Low viscosity
(C) Small latent heat
(D) None of these

12. Ion exchange process is similar to
(A) Absorption
(C) Extraction
(D) Leaching

13. Physical absorption is
(A) An irreversible phenomenon
(B) A reversible phenomenon
(C) Accompanied by evolution of heat
(D) Both (b) and (c)

14. Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the __________ number.
(A) Schmidt
(B) Sherwood
(C) Peclet
(D) Stanton

15. If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is
(A) L/G
(B) G/L
(C) Always < 1
(D) None of these

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