Mass Transfer Chemical Questions & Answers - Set 09

Practice Test: Question Set - 09

1. The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture.
    (A) Composition
    (B) Temperature
    (C) Total pressure
    (D) All (a), (b) and (c)
2. A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids))
    (A) M(Xo - XF)
    (B) M(Xo/XF)
    (C) M ln(Xo/XF)
    (D) MXo ln(Xo/XF)
3. The drying time between fixed moisture content within diffusion controlled 'falling rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid).
    (A) √T
    (B) T
    (C) T2
    (D) T3
4. In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is
    (A) Equal to the heat of formation of surface compound
    (B) Equal to the heat of wetting
    (C) Zero
    (D) Called integral heat of adsorption
5. The critical moisture content in case of drying indicates the __________ rate period.
    (A) Beginning of falling
    (B) Beginning of constant
    (C) End of falling
    (D) None of these
6. Pick out the wrong statement.
    (A) The binary diffusivity in liquids is of the order of 10-5 cm2/sec
    (B) Molecular diffusion in solid is much faster than that in liquids
    (C) Particles movement from higher concentration to lower concentration takes place in diffusion process
    (D) According to Poiseuille's law, the permeability decreases with increase in temperature for flow of a gas through a given capillary
7. Humidity chart is useful for the solution of problems concerning condensation, vaporization and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.
    (A) Molal
    (B) Relative
    (C) Percentage
    (D) None of these
8. Separation of two volatile liquids by distillation makes use of their
    (A) Selectivity
    (B) Relative volatility
    (C) Solubility
    (D) Density difference
9. Powdery materials can be guarded against caking tendency on storage by
    (A) Providing irregular grain size
    (B) Providing minimum percentage of voids
    (C) Having maximum possible points of contact
    (D) None of these
10. The minimum liquid rate to be used in an absorber corresponds to an operating line
    (A) Of slope = 1
    (B) Of slope = 0.1
    (C) Tangential to the equilibrium curve
    (D) None of these
11. Leaching of uranium ore and gold ore is done in
    (A) Centrifugal extractor
    (B) Pachuca tanks
    (C) Bollman extractor
    (D) None of these
12. The slope of the operating line for a single component co-current absorber when plotted in terms of mole ratio units is
    (A) 0
    (B) ∞
    (C) -ve
    (D) +ve
13. For a ternary mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates.
    (A) Binary mixture is represented by the apex
    (B) Binary mixture is represented by any point inside
    (C) Ternary mixture is represented by the sides
    (D) Pure component is represented by the apex
14. In a gas-liquid absorption column, for obtaining the maximum absorption efficiency
    (A) Liquid stream should be distributed uniformly
    (B) Gas stream should be distributed uniformly
    (C) Both gas as well as liquid streams should be distributed uniformly
    (D) By passing should be completely avoided
15. To get high tray efficiency
    (A) Interfacial surface between liquid and gas phase should be large
    (B) Time of contact between the two phases should be less
    (C) Gas velocity should be very low
    (D) Liquid entrainment should be severe
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