Mass Transfer Question Bank Chemical Engineering - Set 30 - ObjectiveBooks

# Practice Test: Question Set - 30

1. Flights in a rotary dryer are provided to
(A) Lift and shower the solids thus exposing it thoroughly to the drying action of the gas
(B) Reduce the residence time of solid
(C) Increase the residence time of the solid
(D) None of these

2. In a forced draft cooling tower, water is cooled from 95 to 80°F by exposure to air with a wet bulb temperature of 70°F. In this case, the
(A) Range is 15°F
(B) Approach is 10°F
(C) Both (a) & (b)
(D) Neither (a) nor (b)

3. To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)
(A) Increase both 'G' and 'S'
(B) Decrease both 'G' and 'S'
(C) Increase 'S' and decrease 'G'
(D) Increase 'G' and decrease 'S'

4. The adiabatic saturation curve for a vapor-gas mixture is
(A) Straight line
(B) Slightly concave upward
(C) Slightly concave downward
(D) None of these

5. For the case of flow of air past a wet bulb thermometer (air water vapor system), the approximate value of h2/ky.Cz is around
(A) 0.60
(B) 0.24
(C) 1
(D) 0.72

6. The temperature to which a vapor gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature.
(A) Dew point
(B) Wet bulb
(C) Dry bulb
(D) None of these

7. Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)
(A) S2/S1
(B) S1/S2
(C) S1 - S2
(D) S1 × S2

8. At what value of reflux ratio, number of theoretical plates in a distillation column is minimum?
(A) 0
(B) 1
(C) ∞
(D) < 1

9. Under conditions of flooding in packed tower, the gas pressure drop
(A) Decreases rapidly
(B) Increases rapidly
(C) Remain constant
(D) Is maximum

10. With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas
(A) Increases
(B) Decreases
(C) Decreases linearly
(D) Remain unaffected

11. Absorption accompanied with chemical reaction is exemplified by the absorption of
(A) Ammonia in water
(B) Benzol present in coke oven gas by wash oil
(C) SO2 in alkaline solution
(D) All (a), (b) and (c)

12. For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as
(A) Re0.33
(B) Re0.53
(C) Re0.83
(D) Re

13. In a counter-current liquid extractor
(A) Both liquids flow at fixed rate
(B) Both liquids can have any desired flow rate
(C) Only one of the liquids may be pumped at any desired rate
(D) Liquid’s flow rate depends upon the temperature and pressure

14. The vapor pressure exerted by the moisture contained in a wet solid depends upon the
(A) Nature of the moisture
(B) Temperature
(C) Nature of the solid
(D) All (a), (b) and (c)

15. In distillation, overhead product contains
(A) Only one component
(B) Two components
(C) Any number of components
(D) Only saturated liquid

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