Mass Transfer Set 18

Mechanical Engineering

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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 18

Q1 | The adiabatic saturation curve for a vapour-gas mixture is
  • Straight line
  • Slightly concave upward
  • Slightly concave downward
  • None of these
Answer: Slightly concave upward
Q2 | For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky .Cz is around
  • 0.6
  • 0.24
  • 1
  • 0.72
Answer: 1
Q3 | The temperature to which a vapour gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature.
  • Dew point
  • Wet bulb
  • Dry bulb
  • None of these
Answer: None of these
Q4 | Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)
  • S2/S1
  • S1/S2
  • S1 - S2
  • S1 × S2
Answer: S1/S2
Q5 | At what value of reflux ratio, number of theoretical plates in a distillation column is minimum?
  • 0
  • 1
  • ?
  • < 1
Answer: ?
Q6 | Under conditions of flooding in packed tower, the gas pressure drop
  • Decreases rapidly
  • Increases rapidly
  • Remain constant
  • Is maximum
Answer: Is maximum
Q7 | With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas
  • Increases
  • Decreases
  • Decreases linearly
  • Remain unaffected
Answer: Decreases
Q8 | Absorption accompanied with chemical reaction is exemplified by the absorption of
  • Ammonia in water
  • Benzol present in coke oven gas by wash oil
  • SO2 in alkaline solution
  • All (A), (B) and (C)
Answer: SO2 in alkaline solution
Q9 | For turbulent mass transfer in pipes, the Sherwood number depends on the Reynoldsnumber as
  • Re0.33
  • Re0.53
  • Re0.83
  • Re
Answer: Re0.83
Q10 | In a counter-current liquid extractor
  • Both liquids flow at fixed rate
  • Both liquids can have any desired flow rate
  • Only one of the liquids may be pumped at any desired rate
  • Liquid’s flow rate depends upon the temperature and pressure
Answer: Only one of the liquids may be pumped at any desired rate
Q11 | The vapour pressure exerted by the moisture contained in a wet solid depends upon the
  • Nature of the moisture
  • Temperature
  • Nature of the solid
  • All (A), (B) and (C)
Answer: All (A), (B) and (C)
Q12 | In distillation, overhead product contains
  • Only one component
  • Two components
  • Any number of components
  • Only saturated liquid
Answer: Any number of components
Q13 | Equilibrium-moisture curves of different solids
  • Are different
  • Are same
  • Depend on the humidity of the gas
  • None of these
Answer: Are different
Q14 | The caking of crystals can be prevented by
  • Maintaining high critical humidity
  • Maintaining low critical humidity
  • Coating the product with inert material
  • Both (A) and (C)
Answer: Both (A) and (C)
Q15 | In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at __________ reflux.
  • Total
  • Minimum
  • Operating
  • Maximum permissible
Answer: Total
Q16 | Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as
  • K ? D
  • K ??D
  • K ? D 1.5
  • K ? D 2
Answer: K ? D
Q17 | Steady state equimolal counter diffusion occurs in case of
  • Leaching
  • Absorption
  • Binary phase distillation
  • Liquid-liquid extraction
Answer: Binary phase distillation
Q18 | On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in
  • Greater degree of separation with a fixed number of trays
  • Increased reboiler load
  • Increased reflux ratio
  • None of these
Answer: Increased reflux ratio
Q19 | __________ is used as an 'entrainer' for the separation of acetic acid-water mixture by distillation.
  • Furfural
  • Benzol
  • Butyl acetate
  • Hexane
Answer: Butyl acetate
Q20 | Mass transfer rate between two fluid phases does not necessarily depend on the __________ of the two phases.
  • Chemical properties
  • Physical properties
  • Degree of turbulence
  • Interfacial area
Answer: Chemical properties
Q21 | If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is
  • 0
  • 1
  • < 1
  • > 1
Answer: 1
Q22 | Which of the following solutions will follow Raoult's law most closely?
  • A solution of benzene, toluene and o-xylene
  • 35% solution of camphor in water
  • 35% solution of NH3 in water
  • A solution of polar organic compounds (not of homologue of a series)
Answer: A solution of benzene, toluene and o-xylene
Q23 | For continuous drying of granular or crystalline material, the dryer used is the __________dryer.
  • Tunnel
  • Tray
  • Rotary
  • None of these
Answer: Rotary
Q24 | Pick out the correct statement.
  • In case of liquid-liquid extraction, no separation is possible, if the selectivity of the solvent used is unity
  • With increase in temperature, the selectivity of the solvent used in solvent extraction decreases
  • The selectivity of solvent used in solvent extraction is unity at the plait point
  • All (A), (B) and (C)
Answer: All (A), (B) and (C)
Q25 | __________ column is preferred to be used, when a high liquid hold up is required in a reactor for gas-liquid reaction.
  • Packed
  • Bubble
  • Spray
  • Tray
Answer: Bubble
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