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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