Mass Transfer Set 4

Mechanical Engineering

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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 4

Q1 | Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture.
  • Unbound
  • Critical
  • Free
  • Bound
Answer: Unbound
Q2 | Swenson-Walker crystalliser is a __________ unit.
  • Continuous
  • Batch
  • Semi-batch
  • Cooling (adiabatic)-cum-evaporation
Answer: Continuous
Q3 | For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be
  • 1
  • 0
  • 2
  • 3
Answer: 1
Q4 | Calculation of mass transfer co-efficient is mostly/normally done using __________ theory.
  • Surface renewal
  • Film
  • Penetration
  • None of these
Answer: Film
Q5 | With increase in temperature, the leaching rate increases because of the
  • Increased diffusivity
  • Decreased viscosity of liquid
  • Both (A) and (B)
  • Neither (A) nor (B)
Answer: Both (A) and (B)
Q6 | Relative volatility varies with the concentration of component for an ideal solution. The relative volatility of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when
  • Only vapor phase follows Raoult's law
  • Only liquid phase obeys Dalton's law
  • Liquid phase obeys Dalton's law and vapor phase obeys Raoult's law
  • Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law
Answer: Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law
Q7 | Which one of the following devices is not used for both the absorption as well as the liquidliquid extraction processes?
  • Packed towers
  • Plate towers
  • Spray towers
  • Wetted wall columns
Answer: Wetted wall columns
Q8 | Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as
  • K ?D
  • K ??D
  • K ?D 1.5
  • K ?D 2
Answer: K ??D
Q9 | Pick out the wrong statement.
  • Mechanical agitation is required, if the system has low interfacial tension
  • Sieve tray towers are generally used for systems having low interfacial tension
  • When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance
  • Taylor-Prandtl analogy for heat and mass tr
Answer: When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance
Q10 | For water-ethanol system, the minimum reflux ratio
  • Is computed from the slope of the upper operating line that is tangent to the equilibrium curve
  • Is computed from the intercept of the operating line
  • Cannot be computed
  • Is the optimum reflux ratio
Answer: Is computed from the slope of the upper operating line that is tangent to the equilibrium curve
Q11 | Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation?
  • Cost
  • Availability
  • Toxicity
  • Selectivity
Answer: Selectivity
Q12 | At 750°K and 1 atm, the approximate value of Schmidt number for air is
  • 0.01
  • 0.1
  • 1
  • 10
Answer: 0.1
Q13 | What is the degree of freedom of an absorption process in which only one component is transferred between phases?
  • 1
  • 2
  • 3
  • 4
Answer: 3
Q14 | Rayleigh equation applies to __________ distillation.
  • Differential
  • Flash
  • Equilibrium
  • Molecular
Answer: Differential
Q15 | In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as
  • KG = 1/KG + m/KL
  • 1/KG = 1/KG + m/KL
  • 1/KG = 1/KL + m/KG
  • KG = 1/KL + m/KG
Answer: 1/KG = 1/KG + m/KL
Q16 | Leaching of coarse solid lumps is also termed as
  • Decoction
  • Dissolution
  • Percolation
  • Agitation and settling
Answer: Percolation
Q17 | Which of the following can be calculated theoretically using steam table and Dalton's law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known?
  • Dew point
  • Humidity ratio
  • Wet bulb temperature
  • None of these
Answer: Wet bulb temperature
Q18 | Danckwerts developed the __________ theory.
  • Penetration
  • Surface renewal
  • Film
  • None of these
Answer: Surface renewal
Q19 | Steam distillation is used to
  • Reduce the number of plates
  • Avoid thermal decomposition of a component
  • Increase the efficiency of separation
  • Increase the total pressure of distillation
Answer: Avoid thermal decomposition of a component
Q20 | When an unsaturated air-water mixture is heated at constant pressure, then
  • The partial pressure of water vapour increases
  • The specific humidity decreases
  • The relative humidity increases
  • The relative humidity decreases
Answer: The relative humidity decreases
Q21 | Flash distillation is
  • Same as differential distillation
  • Used for multi-component systems like crude refining
  • Same as simple distillation
  • Most useful for handling binary systems
Answer: Used for multi-component systems like crude refining
Q22 | Mechanism of moisture removal in case of freeze drying of food stuff is by
  • Evaporation
  • Sublimation
  • Dehydration
  • Adsorption
Answer: Sublimation
Q23 | Molality is defined as the number of gm moles of solute per __________ of solvent.
  • Litre
  • gm
  • Kg
  • m3
Answer: Kg
Q24 | When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation.
  • Continuous
  • Steam
  • Azeotropic
  • None of these
Answer: Steam
Q25 | Alcohol is dehydrated using __________ distillation.
  • Extractive
  • Azeotropic
  • Steam
  • Molecular
Answer: Azeotropic
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