Mass Transfer Exam Questions - Set 18 - ObjectiveBooks

# Practice Test: Question Set - 18

1. Pick out the wrong statement.
(A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one
(B) Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference
(C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(b)P - 3, Q - 2
(D) The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

2. According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity).
(A) D
(B) D2
(C) D0.5
(D) 1/D

3. For a distillation column operating at minimum reflux, the
(A) Concentration of liquid and vapor leaving a plate will be same
(B) Reflux ratio will be maximum
(C) Number of plates required will be maximum
(D) None of these

4. Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2. hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is
(A) 25%
(B) 50%
(C) 70%
(D) 90%

5. Mass transfer co-efficient is directly proportional to DAB0.5, according to __________ theory.
(A) Penetration
(B) Surface renewal
(C) Film
(D) None of these

6. Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty?
(A) Grid tray tower
(B) Perforated tray tower
(C) Wetted wall tower
(D) Bubble cap tower

7. For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is
(A) Calculated
(B) Unknown
(C) Known
(D) Not required

8. With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency
(A) Increases
(B) Decreases
(C) Remain same
(D) May increase or decrease; depends on individual design

9. Diameter to height ratio for a raschig ring is
(A) 1
(B) 0.5
(C) 2
(D) 8

10. Which of the following operations does not involve leaching?
(A) Dissolving gold from ores
(B) Dissolving pharmaceutical products from bark or roots
(C) Dissolving sugar from the cells of the beet
(D) Removing nicotine from its water solution by kerosene

11. Flooding in a distillation column is detected by a sharp
(A) Increase in Murphree plate efficiency
(B) Decrease in pressure drop
(C) Decrease in liquid hold up in the column
(D) Increase in pressure drop

12. In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction,
(A) Inversely
(B) Linearly
(C) Exponentially
(D) None of these

13. With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system).
(A) Increases
(B) Decreases
(C) Remain unaffected
(D) Increases Linearly

14. Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if
(A) Mass transfer is accompanied by reaction
(B) Diffusion of A is in stagnant medium B
(C) Molecular mean free path is high
(D) There is equimolar counter diffusion

15. Absorption accompanied by heat evolution results in
(A) Increased capacity of the absorber
(B) Increase in equilibrium solubility
(C) Decrease in equilibrium solubility
(D) None of these

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