Chemical Engineering Mass Transfer One Mark Questions - Set 22 - ObjectiveBooks

Chemical Engineering Mass Transfer One Mark Questions - Set 22

Practice Test: Question Set - 22

1. The 'shanks system' of leaching (i.e., counter-current multiple contact leaching) is used for
    (A) Recovery of tannis from the tree barks and woods
    (B) Leaching sodium nitrate from Chilean nitrate bearing rock
    (C) Both (a) and (b)
    (D) Neither (a) nor (b)

2. The value of Lewis number (Le = Sc/Pr) for air-water vapor system is around
    (A) 1
    (B) 0.24
    (C) 3.97
    (D) 600

3. Which of the following employs an accessory known as 'drift eliminator'?
    (A) Multiple effect evaporator
    (B) Mechanical draft cooling tower
    (C) Rotary dryer
    (D) Rotating disc contactor

4. Dew point of an air-water vapor mixture
    (A) Decreases with decrease in pressure
    (B) At constant humidity & total pressure is fixed
    (C) Corresponding to any point on the humidity chart is obtained by projecting a line through this point parallel to the temperature axis and to the saturation curve
    (D) All 'a', 'b' & 'c'

5. The term "approach" in a cooling tower refers to the difference in the temperature of the
    (A) Cold water leaving the tower and the wet bulb temperature of the surrounding air
    (B) Hot water entering the tower and the wet bulb temperature of the surrounding air
    (C) Hot water entering and the cooled water leaving the cooling tower
    (D) None of these

6. The relation, Sc = Pr = 1, is valid, when the mechanism of __________ transfer is same.
    (A) Heat and mass
    (B) Mass and momentum
    (C) Heat and momentum
    (D) Heat, momentum and mass

7. The surface renewal frequency in Danckwerts' model of mass transfer is given by (KL: mass transfer co-efficient)
    (A) √(KL2.DA)
    (B) KL2.DA
    (C) KL2/DA
    (D) KL/DA2

8. McCabe-Thiele method
    (A) Uses molal units for material and energy balance
    (B) Uses weight fractions to express liquid and vapor composition
    (C) Can use any type of units
    (D) Is more accurate than Ponchon-Savarit method

9. Below is given an equilibrium moisture curve of a substance. State which regions represent free moisture and unbound moisture respectively.

Mass Transfer - Set 22, Question No. 09
    (A) II, III
    (B) II, IV
    (C) IV, III
    (D) IV, II

10. If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent.
    (A) 100
    (B) > 100
    (C) < 100
    (D) None of these

11. Humid volume, at a given temperature is a/an __________ function of humidity.
    (A) Inverse
    (B) Exponential
    (C) Linear
    (D) Logarithmic

12. If the specific heats of a gas and a vapor are 0.2KJ/Kg.°K and 1.5 KJ/Kg.°K respectively, and the humidity is 0.01; the humid heat in KJ/°Kg. is
    (A) 0.31
    (B) 0.107
    (C) 0.017
    (D) 0.215

13. Flooding in a vapor-liquid contacting equipment occurs in a tray, when the pressure drop through a tray is __________ the liquid head available in the downcomer.
    (A) Less than
    (B) More than
    (C) Same as
    (D) Very much less

14. In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated.
    (A) Molecular
    (B) Azeotropic
    (C) Extractive
    (D) Flash

15. Pick out the wrong statement.
    (A) Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the possibility of tower wall collapse
    (B) Packed towers are preferred over plate towers for handling corrosive and foamy liquids
    (C) Diameter of randomly packed tower is normally more than 1.2 meters
    (D) Due to uneven supply and improper distribution of liquid, problem of channelling, loading & flooding is generally encountered in packed towers

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