Mass Transfer Set 8

Mechanical Engineering

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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 8

Q1 | With increase in temperature, the mutual solubility of two liquids
  • Increases
  • Decreases
  • Remains unchanged
  • Decreases exponentially
Answer: Increases
Q2 | The operating cost of a distillation column at minimum reflux ratio is
  • Minimum
  • Maximum
  • Infinite
  • Zero
Answer: Minimum
Q3 | For a single component absorber, the operating line is straight only when plotted in term of __________ units.
  • Partial pressure
  • Mole ratio
  • Mole fraction
  • None of these
Answer: Mole ratio
Q4 | The cooling effect in a cooling tower cannot be increased by
  • Increasing the air velocity over the wet surfaces
  • Reducing the humidity of entering air
  • Lowering the barometric pressure
  • None of these
Answer: None of these
Q5 | Separation of __________ employs gaseous diffusion process.
  • N2 and O2 from air
  • Isotopes of uranium
  • Isotopes of helium
  • SO2 and air
Answer: Isotopes of uranium
Q6 | Sodium bicarbonate is produced during soda ash manufacture using a __________ tower.
  • Plate
  • Baffle
  • Packed
  • None of these
Answer: Baffle
Q7 | Leaching rate is independent of the
  • Agitation
  • Temperature
  • Particle size
  • None of these
Answer: None of these
Q8 | With increase in temperature, the rate of leaching increases, because the
  • Diffusivity of solute increases
  • Viscosity of solvent decreases
  • Thermal conductivity of solute increases
  • None of these
Answer: Diffusivity of solute increases
Q9 | Bound moisture is that liquid which exerts an equilibrium vapor pressure __________ that of the pure liquid at the given temperature.
  • Less than
  • More than
  • Equal to
  • Either (A) or (B); depends on the solid
Answer: Less than
Q10 | The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is
  • 2
  • 0.5
  • 50
  • 150
Answer: 2
Q11 | Which of the following is not a batch drier?
  • Truck drier
  • Agitated pan drier
  • Fluidised bed drier
  • Vacuum shelf drier
Answer: Fluidised bed drier
Q12 | Acetic acid will be most economically separated from a dilute solution of acetic acid in water by
  • Solvent extraction
  • Continuous distillation
  • Evaporation
  • Absorption
Answer: Solvent extraction
Q13 | The main reason for dividing a tall packed tower into series of small towers is to
  • Minimise the overall pressure drop
  • Avoid flooding
  • Reduce liquid hold up
  • Avoid channelling
Answer: Avoid channelling
Q14 | The most efficient cooling tower out of the following is
  • Induced draft
  • Forced draft
  • Natural draft
  • Atmospheric
Answer: Induced draft
Q15 | Molecular distillation is
  • High temperature distillation
  • For heat-sensitive materials
  • Very low pressure distillation
  • Both (B) and (C)
Answer: Both (B) and (C)
Q16 | The value of NA/(NA + NB) for steady state molecular diffusion of gas 'A' through nondiffusing gas 'B' is
  • 1
  • ?
  • 0.5
  • 2
Answer: 1
Q17 | All moisture in a non-hygroscopic material is the __________ moisture.
  • Free
  • Equilibrium
  • Unbound
  • Bound
Answer: Unbound
Q18 | Molecular diffusivity of a liquid
  • Increases with temperature
  • Decreases with temperature
  • May increase or decrease with temperature
  • Is independent of temperature
Answer: Increases with temperature
Q19 | Raschig ring made of porcelain cannot be used for treating concentrated
  • Hydrochloric acid
  • Nitric acid
  • Alkalis
  • Sulphuric acid
Answer: Alkalis
Q20 | Use of natural draft cooling tower is practised, when the air has low
  • Humidity
  • Temperature
  • Both 'a' & 'b'
  • Neither 'a' nor 'b'
Answer: Both 'a' & 'b'
Q21 | At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent.
  • 100
  • zero
  • 50
  • Between 0 and 100
Answer: zero
Q22 | Tower diameter may be decreased by
  • Using higher reflux ratio
  • Use of increased tray spacing
  • Increasing the liquid flow rate
  • Increasing the vapour flow rate
Answer: Use of increased tray spacing
Q23 | Pick out the wrong statement.
  • The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr= 1
  • 1 Nm3 of dry air is lighter than 1Nm3 of humid air
  • The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity
  • An Azeotropic mixture of two liquids has boiling point higher than either of them, when it shows negative deviation from Raoult's Law
Answer: 1 Nm3 of dry air is lighter than 1Nm3 of humid air
Q24 | The humid volume may be increased by increasing the
  • Temperature at constant humidity
  • Humidity at constant temperature
  • Both (A) and (B)
  • Neither (A) nor (B)
Answer: Both (A) and (B)
Q25 | Pick out the correct relationship. (Where, Ri = internal reflux ratio Ro = external reflux ratio.)
  • (1 + Ro) = Ro/Ri
  • (1 - Ro) = Ro/Ri
  • (1 + Ri) = Ro/Ri
  • (1 - Ri) = Ro/Ri
Answer: (1 + Ro) = Ro/Ri
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