Practice Test: Question Set - 27
1. Ordinary diffusion process is also called __________ diffusion.
- (A) Pressure
- (B) Thermal
- (C) Concentration
- (D) Forced
2. The falling rate period in the drying of a solid is characterized by
- (A) Increase
in rate of drying
- (B) Increasing
temperatures both on the surface and within the solid
- (C) Decreasing
temperatures
- (D) None of these
3. Decoction refers to the use of solvent
- (A) At
ambient temperature
- (B) At
its boiling point
- (C) In
its vapor form
- (D) None of these
4. Schmidt number and Lewis number for pure air at atmospheric conditions are respectively
- (A) < 1 and ≈ 1
- (B) 1 and 0
- (C) > 1 and ≈ 1
- (D) 0 and ≈ 1
5. Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.
- (A) Wetted wall
- (B) Bubble cap
- (C) Perforated tray
- (D) Packed
6. Pick out the correct statement.
- (A) For
identical gas flow rates, less pressure drop occurs through a plate tower than
through a packed tower
- (B) Plate column can
handle greater liquid loads without flooding than packed column, but the liquid
hold up is more in the case of plate column
- (C) For
the same duty, plate columns weigh less than packed columns
- (D) All (a), (b) and (c)
7. The solvent used in liquid-liquid extraction should have __________ less than one.
- (A) Selectivity
- (B) Distribution
co-efficient
- (C) Both (a) and (b)
- (D) Neither (a) nor (b)
8. Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the
- (A) Mass transfer
co-efficient
- (B) Thermal diffusivity
- (C) Kinematic viscosity
- (D) Volumetric
diffusivity
9. Pick out the wrong statement.
- (A) Different solids have
different equilibrium moisture curves
- (B) Total condenser or
reboiler is considered equivalent to one theoretical plate in McCabe-Thiele
method of theoretical plate calculation for distillation column
- (C) Heat removal load on
cooler remains constant, even with increase of the reflux ratio in a
distillation column
- (D) Even a forced draft
cooling tower cannot cool water below the wet bulb temperature
10. Which of the following equipments is not used for liquid dispersion?
- (A) Wetted wall towers
- (B) Packed towers
- (C) Venturi scrubbers
- (D) Agitated vessels
11. The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm2/sec.
- (A) 0.25
- (B) 2.5
- (C) 1.25
- (D) 0.0025
12. Molecular diffusion is caused by the
- (A) Transfer
of molecules from low concentration to high concentration region
- (B) Thermal energy of the
molecules
- (C) Activation energy of
the molecules
- (D) Potential energy of
the molecules
13. Liquid diffusivity is of the order of __________ cm2 /second.
- (A) 0.01
- (B) 0.1
- (C) 10-5 to
10-6
- (D) > 1
14. The diffusivity, DAB (for component A diffusing in B) is equal to the diffusivity DBA (for component B diffusing in A) for a binary mixture of
- (A) Newtonian liquids
- (B) Non-Newtonian liquids
- (C) Ideal gases
- (D) Real gases
15. Can a cooling tower cool water below the wet bulb temperature of inlet air?
- (A) Yes
- (B) No
- (C) Yes; but height of
cooling tower will be prohibitively high
- (D) Yes; but the air flow
rate should be excessively high
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