Mass Transfer Set 23

Mechanical Engineering

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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 23

Q1 | Gaseous diffusion co-efficient increases with increase in the
  • Pressure
  • Temperature
  • Both (A) & (B)
  • Neither (A) nor (B)
Answer: Temperature
Q2 | Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted)represent
  • A pure component
  • A binary mixture
  • A ternary mixture
  • Partially miscible ternary system
Answer: A binary mixture
Q3 | The rate of mass transfer is not dependent upon the
  • Degree of dispersion of one fluid in the other
  • Interfacial surface exposed between the phases
  • Both (A) & (B)
  • None of these
Answer: None of these
Q4 | Air at a particular humidity is heated in a furnace. The new dew point
  • Decreases
  • Increases
  • Depends on the extent of heating
  • Remain unchanged
Answer: Increases
Q5 | The rate of solid-liquid extraction is limited by the
  • Phase change of the solute as it dissolves in the solvent
  • Diffusion of the solute through the solvent in the pores to the outside of the particle
  • Diffusion of the solute from the solution in contact with the particle to the main bulk of the solution
  • All 'a', 'b' & 'c'
Answer: All 'a', 'b' & 'c'
Q6 | In case of gases, the binary diffusivity is proportional to (where, P = pressure).
  • P
  • 1/P
  • 1/?P
  • ?P
Answer: 1/P
Q7 | One mole feed of a binary mixture of a given composition is flash vaporised at a fixed P and T. If Raoult's law is obeyed, then changing the feed composition would effect
  • The product composition but not the fraction vaporised
  • The product composition as well as the fraction vaporised
  • The fraction vaporised but not the product composition
  • Neither the product composition nor the fraction vaporised
Answer: The fraction vaporised but not the product composition
Q8 | What is the reflux ratio at total reflux?
  • Zero
  • Infinity
  • Unity
  • Data insufficient
Answer: Infinity
Q9 | The operating line for an absorber is curved, when plotted in terms of
  • Mole fractions
  • Mole ratios
  • Partial pressure
  • Mass fractions
Answer: Partial pressure
Q10 | Which of the following is the most suitable for extraction in a system having very lowdensity difference?
  • Mixer-settler extractor
  • Centrifugal extractor
  • Pulsed extractor
  • Packed extraction tower
Answer: Centrifugal extractor
Q11 | (NSh/NRe.NSc) is termed in mass transfer operation as the
  • Stanton number
  • Peclet number
  • Thermal diffusivity
  • Momentum diffusivity
Answer: Stanton number
Q12 | In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase.
  • Gas
  • Liquid
  • Both (A) & (B)
  • Neither (A) nor (B)
Answer: Liquid
Q13 | Positive deviation from Raoult's law means a mixture whose total pressure is
  • Greater than that computed for ideality
  • Less than that computed for ideality
  • Less than the sum of the vapour pressure of the components
  • None of these
Answer: Greater than that computed for ideality
Q14 | Flooding results in
  • High tray efficiency
  • Low tray efficiency
  • High gas velocity
  • Good contact between the fluids
Answer: Low tray efficiency
Q15 | At minimum reflux ratio for a given separation
  • Number of plates is zero
  • Number of plates is infinity
  • Minimum number of the theoretical plates is required
  • Separation is most efficient
Answer: Number of plates is infinity
Q16 | An ideal tower packing should not
  • Have low weight per unit volume
  • Have large surface area per unit volume
  • Have large free cross-section
  • Hold up large amount of liquid in the packing
Answer: Hold up large amount of liquid in the packing
Q17 | Diffusion in concentrated solutions differs from that in dilute solutions, because of the change in the __________ with the concentration of the solution.
  • Degree of ideality
  • Viscosity
  • Both 'a '& 'b'
  • Neither 'a' nor 'b'
Answer: Both 'a '& 'b'
Q18 | Make up water is supplied during cooling tower operation to compensate for water losses due to
  • Evaporation
  • Blowdown
  • Entrainment
  • All (A), (B) & (C)
Answer: All (A), (B) & (C)
Q19 | The dimension of diffusivity is same as that of the
  • Density
  • Molal concentration
  • Kinematic viscosity
  • Velocity head
Answer: Kinematic viscosity
Q20 | As the reflux ratio in a distillation column is increased from the minimum, the
  • Slope of the operating line in stripping section decreases
  • Number of plates decreases very slowly first and then more and more rapidly
  • Total cost first decreases and then increases
  • Liquid flow increases while the vapor flow decreases for a system
Answer: Total cost first decreases and then increases
Q21 | Fenske-Underwood equation used for calculating the minimum number of theoreticalplates in distillation column is valid for
  • Constant molal overflow
  • Total reflux
  • Constant relative volatility
  • All (A), (B) and (C)
Answer: All (A), (B) and (C)
Q22 | Solvent used in extractive distillation
  • Is of low volatility
  • Forms a low boiling azeotrope
  • Forms a high boiling azeotrope
  • Does not alter the relative volatility of the original components
Answer: Forms a low boiling azeotrope
Q23 | When the feed to a distillation column is a saturated liquid, slope of the feed line is
  • Zero
  • Unity
  • Infinity
  • None of these
Answer: Infinity
Q24 | The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and, m = slope of the equilibrium line).
  • L/mG
  • G/mL
  • mL/G
  • LG/m
Answer: L/mG
Q25 | Chemisorption (chemical adsorption) is
  • Same as "Van der Waals" adsorption
  • Characterised by adsorption of heat
  • An irreversible phenomenon
  • A reversible phenomenon
Answer: An irreversible phenomenon
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