Mass Transfer Set 2

Mechanical Engineering

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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 2

Q1 | The commonly used solvent in supercritical extraction is
  • Methyl ethyl ketone
  • Water
  • Carbon tetrachloride
  • Carbon dioxide
Answer: Carbon dioxide
Q2 | Dried finished product sampled from various parts of a __________ dryer exhibits nonuniformity in the moisture content.
  • Rotary
  • Tray
  • Freeze
  • None of these
Answer: Tray
Q3 | For the same system, if the same liquid used in an absorber is decreased, the tower height will
  • Increase
  • Decrease
  • Remain unaffected
  • Decrease or increase; depends on the type of liquid
Answer: Increase
Q4 | In steam distillation, the
  • Temperature is 100°C
  • Temperature is more than 100° C
  • Product must be immiscible with water
  • Temperature is higher than the boiling point of either component
Answer: Product must be immiscible with water
Q5 | The equation, NA = (DAB . Pt /RTZ . PBM) (PA1 - PA2) is for
  • Fick's second law of diffusion
  • Steady state diffusion for stagnant case
  • Liquid M.T.C. by Higbie penetration theory
  • None of these
Answer: Steady state diffusion for stagnant case
Q6 | A slurry is to be dried to produce flaky solid. Which dryer would you recommend?
  • Spray dryer
  • Drum dryer
  • Rotary dryer
  • Dielectric dryer
Answer: Spray dryer
Q7 | Perforated plate towers are unique for solvent extraction because, they provide
  • Higher contact area
  • Better contact of the phase
  • Repeated coalescence & redispersion of the drop phase
  • None of these
Answer: Repeated coalescence & redispersion of the drop phase
Q8 | Which of the following parameters remains constant during chemical dehumidification?
  • Dry bulb temperature
  • Partial pressure of vapour
  • Wet bulb temperature
  • None of these
Answer: Dry bulb temperature
Q9 | For the gas absorption, the height of a transfer unit, based on the gas phase is given by (G: superficial molar gas velocity, L: superficial molar liquid velocity, FG: mass transfer co-efficient, moles/m2, a: interfacial area per unit volume of tower)
  • G/(FG . a)
  • FG/(G . a)
  • (G . a)/FG
  • L/(FG . G)
Answer: G/(FG . a)
Q10 | Coffee is prepared from coffee beans by leaching with
  • Cold water
  • Hot water
  • Dilute hot caustic solution
  • Naphtha
Answer: Hot water
Q11 | Pore size of the molecular sieve 5A is __________ mm.
  • 5
  • 0.5
  • 0.05
  • 50
Answer: 0.5
Q12 | The equation, NA = (DAB . Pt /RTZ) (y1 - y2) is for
  • Steady state equimolar counter diffusion
  • Fick's first law of diffusion
  • Steady state diffusion for stagnant case
  • Liquid M.T.C. by penetration theory
Answer: Steady state equimolar counter diffusion
Q13 | To remove all the moisture from a wet solid it requires exposure to __________ air.
  • Perfectly dry
  • Highly humid
  • High temperature
  • None of these
Answer: Perfectly dry
Q14 | Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)
  • (De.t)1/2
  • (De/t)1/2
  • (4De/?t)1/2
  • (4De/t)
Answer: (4De/?t)1/2
Q15 | The cooling effect in a cooling tower can be speeded up by
  • Increasing the air velocity and area of exposed wet surface
  • Reducing the barometric pressure
  • Reducing the humidity of the air
  • All (A), (B) and (C)
Answer: All (A), (B) and (C)
Q16 | The relative volatility of a binary mixture at the Azeotropic composition is
  • 1
  • > 1
  • ?
Answer: 1
Q17 | Which of the following processes is not an example of adsorption applied to gaseous separations?
  • Recovery of valuable solvent vapors from dilute mixture with air and other gases
  • Dehumidification of air and gas
  • Removal of objectionable odour and impurities from industrial gases
  • Decolouration of yellow glycerine
Answer: Decolouration of yellow glycerine
Q18 | For absorbing a sparingly soluble gas in a liquid, the
  • Gas side co-efficient should be increased
  • Liquid side coefficient should be increased
  • Gas side co-efficient should be decreased
  • Liquid side co-efficient should be decreased
Answer: Liquid side coefficient should be increased
Q19 | The Knudsen diffusivity is proportional to (where, T = absolute temperature)
  • ?T
  • T2
  • T
  • T4
Answer: ?T
Q20 | Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture.
  • Free
  • Unbound
  • Equilibrium
  • Bound
Answer: Equilibrium
Q21 | For the flow of gases through a capillary, with increase in temperature, the permeability__________ as per Knudsen law.
  • Increases
  • Decreases
  • Remain same
  • Either (A) or (B); depends on the gas
Answer: Increases
Q22 | A natural draft cooling tower is filled with wooden grids, which covers about __________percent of the tower height.
  • 15-Oct
  • 30-40
  • 70-80
  • 90-100
Answer: 15-Oct
Q23 | With increase in the liquid flow rate at a fixed gas velocity in a randomly packed countercurrent gas-liquid absorption column, the gas pressure drop
  • Decreases
  • Remains unchanged
  • Increases
  • Decreases exponentially
Answer: Increases
Q24 | Which of the following is not fixed by the process requirements, in the design of absorbers?
  • Flow rate of the entering gas
  • Composition of the entering liquid
  • Terminal concentrations of gas stream
  • None of these
Answer: None of these
Q25 | Pick out the wrong statement:
  • Absorption factor is constant, when the equilibrium and operating lines are straight
  • In case of a stripper, the equilibrium curve is always below the operating line
  • In case of an absorber, the operating line is always above the equilibrium curve
  • In the absorption of low solubility gases, the liquid film is the controlling resistance
Answer: In case of a stripper, the equilibrium curve is always below the operating line
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