Fundamentals of Mass Transfer MCQ Test - Set 04 - ObjectiveBooks
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# Practice Test: Question Set - 04

1. The Knudsen diffusivity is proportional to (where, T = absolute temperature)
(A) √T
(B) T2
(C) T
(D) T4

2. Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture.
(A) Free
(B) Unbound
(C) Equilibrium
(D) Bound

3. For the flow of gases through a capillary, with increase in temperature, the permeability __________ as per Knudsen law.
(A) Increases
(B) Decreases
(C) Remain same
(D) Either (a) or (b); depends on the gas

4. A natural draft cooling tower is filled with wooden grids, which covers about __________ percent of the tower height.
(A) 10-15
(B) 30-40
(C) 70-80
(D) 90-100

5. With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop
(A) Decreases
(B) Remains unchanged
(C) Increases
(D) Decreases exponentially

6. Which of the following is not fixed by the process requirements, in the design of absorbers?
(A) Flow rate of the entering gas
(B) Composition of the entering liquid
(C) Terminal concentrations of gas stream
(D) None of these

7. Pick out the wrong statement:
(A) Absorption factor is constant, when the equilibrium and operating lines are straight
(B) In case of a stripper, the equilibrium curve is always below the operating line
(C) In case of an absorber, the operating line is always above the equilibrium curve
(D) In the absorption of low solubility gases, the liquid film is the controlling resistance

8. Which of the following processes is followed by unsaturated air (with dry bulb temperature 12°C and relative humidity 47%) passing through water spray washer (temperature of water being constant at 40°C?
(A) Humidification only
(B) Heating only
(C) Both heating and humidification
(D) Evaporative cooling

9. The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if
(A) NSc = 1
(B) NSc = NPr = NLe
(C) NPr = NLe
(D) NSc = NLe

10. Pick out the wrong statement. Generally for physical adsorption, a gas of
(A) Higher molecular weight is adsorbed in preference to a gas of low molecular weight
(B) High critical temperature is adsorbed in preference to a gas of low critical temperature
(C) Low volatility is adsorbed in preference to a gas of high volatility
(D) None of these

11. Co-current absorbers are usually used when the gas to be dissolved in the liquid is
(A) Sparingly soluble
(B) Highly soluble
(C) A pure substance
(D) A mixture

12. Molecular sieves are regenerated by heating to __________ °C.
(A) < 150
(B) 200-330
(C) > 500
(D) > 1000

13. In triangular co-ordinates, the ternary composition point falls __________ of the triangle.
(A) In the corners
(B) Inside
(C) On the sides
(D) None of these

14. When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30°C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system,
(A) As the acetone concentration increases, the solubility curves approach each other
(B) Both the phases become identical at a particular common point on both the solubility curves called the plait point
(C) The distribution curve which is a plot between x (acetone concentration in one phase) and y (acetone concentration in other phase) is analogous to x-y curve used in distillation and absorption terminates on the x = y diagonal at the concentration of the plait point
(D) All (a), (b) and (c)

15. During sensible cooling process
(A) Relative humidity decreases
(B) Relative humidity increases
(C) Wet bulb temperature decreases
(D) Both (b) and (c)

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