Mass Transfer Chemical Engineering MCQ Test - Set 02 - ObjectiveBooks

Practice Test: Question Set - 02

1. 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:

(A) 5.6 × 10-4
(B) 8.5 × 10-4
(C) 5.6 × 10-3
(D) 8.5 × 10-3

2. In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number.

(A) Lewis
(B) Grashoff
(C) Sherwood
(D) None of these

3. When the gas to be dissolved in liquid is a/an __________ then normally co-current adsorber are used.

(A) Mixture of two gases
(B) Pure gas
(C) Ideal gas
(D) Sparingly soluble gas

4. Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be

(A) Cooled
(B) Humidified
(C) Both (a) & (b)
(D) Dehumidified

5. __________ equation applies to diffusivities in liquids.

(A) Gilliland
(B) Hirschfelder
(C) Wilke and Chang
(D) None of these

6. Mass transfer co-efficient is defined as

(A) Flux = Co-efficient/concentration difference
(B) Co-efficient = Flux/concentration difference
(C) Flux=concentration difference/coefficient
(D) None of these

7. The relative volatility of a binary mixture at constant temperature __________ the total pressure.

(A) Decreases with increase in
(B) Increases with increase in
(C) Is independent of
(D) None of these

8. Large quantity of silica gel is normally dried in a __________ dryer.

(A) Freeze
(B) Through circulation
(C) Rotary vacuum
(D) Tray

9. The mass transfer co-efficient for a solid sphere of radius 'a' dissolving in a large volume of quiescent liquid, in which ‘D’ is the diffusivity of solute, is

(A) D/a
(B) D/2a
(C) Proportional to √D
(D) Dependent on the Reynolds number

10. The value of ‘L/mG’ ratio for economical absorption operation ranges from

(A) 0.5 to 0.8
(B) 0.8 to 1.2
(C) 1.25 to 2.0
(D) 2.5 to 3.5

11. Cox chart, which is useful in the design of distillation column particularly for petroleum hydrocarbons, is a plot of (where, P = vapor pressure, T = temperature).

(A) log P vs. T
(B) log P vs. log T
(C) T vsP
(D) P vs. log T

12. In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raffinate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg)

(A) 6.89
(B) 8.89
(C) 10
(D) 8.25

13. The commonly used solvent in supercritical extraction is

(A) Methyl ethyl ketone
(B) Water
(C) Carbon tetrachloride
(D) Carbon dioxide

14. Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.

(A) Rotary
(B) Tray
(C) Freeze
(D) None of these

15. For the same system, if the same liquid used in an absorber is decreased, the tower height will

(A) Increase
(B) Decrease
(C) Remain unaffected
(D) Decrease or increase; depends on the type of liquid

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