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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 25
Q1 | If a two phase system is in physical equilibrium; then it means that, the
- Escaping tendency of each component from the liquid phase to the vapor phase is exactly equal to that from vapor phase to liquid phase
- Temperature of the liquid phase is equal to that of the vapor phase
- Total pressure throughout the liquid phase is equal to that throughout the vapor phase
- All (A), (B) and (C)
Q2 | Which of the following remains constant during evaporative cooling process with recirculated water supply?
- Relative humidity
- Partial pressure of vapour
- Wet bulb temperature
- None of these
Q3 | Weight of 1 m3 of humid air as compared to 1 m3 of dry air, under the same conditions, is
- Less
- More
- Same
- Unpredictable
Q4 | Solvent used in extractive distillation
- Changes the relative volatility of the original components
- Should be of high volatility
- Should form azeotropes with the original components
- All (A), (B) and (C)
Q5 | The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is
- Natural draft cooling tower
- Induced draft cooling tower
- Spray chamber
- None of these
Q6 | CO2 can be absorbed by
- Hot cupric oxide
- Heated charcoal
- Cold Ca(OH)2
- Alumina
Q7 | The Knudsen diffusivity is dependent on the
- Molecular velocity only
- Pore radius of the catalyst only
- Molecular mean free path only
- Molecular velocity and pore radius of the catalyst
Q8 | Critical humidity of a solid salt means the humidity
- Above which it will always become damp
- Below which it will always stay dry
- Both (A) and (B)
- Above Which it will always become dry and below which it will always stay damp
Q9 | For a binary mixture with low relative volatility, continuous rectification to get pure products will require
- Low reflux ratio
- Less number of trays
- Small cross-section column
- High reflux ratio
Q10 | Overall efficiency of the distillation column is
- The ratio of number of ideal plates to actual plates
- The ratio of number of actual plates to ideal plates
- Same as the Murphree efficiency
- Always more than the point efficiency
Q11 | The binary diffusivity in gases does not depend upon the
- Pressure
- Temperature
- Nature of the components
- None of these
Q12 | Diffusivity in concentrated solutions differs from that in dilute solutions, because of the changes in
- Viscosity with concentration
- Degree of ideality of the solution
- Both (A) and (B)
- Neither (A) nor (B)
Q13 | The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are
- Parallel
- Straight
- Both parallel and straight
- Neither parallel nor straight
Q14 | For contacting a highly soluble gas with a liquid
- Bubble the gas through liquid
- Spray the liquid on gas stream
- Either (A) or (B) would suffice
- None of these
Q15 | Which of the following remains constant during sensible cooling process?
- Specific humidity
- Partial pressure of vapour
- Both (A) and (B)
- Neither (A) nor (B)
Q16 | In saturated gas, the
- Vapour is in equilibrium with the liquid at the gas temperature
- Vapour is in equilibrium with the liquid at the room temperature
- Partial pressure of vapour equals the vapour pressure of the liquid at room temperature
- None of these
Q17 | In a counter-current extractor, as the axial mixing increases, the extraction efficiency
- Increases
- Decreases
- Remains unchanged
- Depends on the pressure of the system
Q18 | At equilibrium the concentration of water in vapour phase (C*) in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is
- 0
- 0.2
- 0.4
- 1
Q19 | In case of absorption with exothermic reaction, for fluids having
- Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence
- Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same
- Both (A) and (B)
- Pr = Sc; there won't be any change in heat and mass tr
Q20 | Drying operation under vacuum is carried out to
- Dry those materials which have very high unbound moisture content
- Reduce drying temperature
- Increase drying temperature
- Dry materials having high bound moisture content
Q21 | Sticky material can be dried in a __________ dryer.
- Tray
- Rotary
- Fluidised bed
- None of these
Q22 | The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid).
- ?T
- T
- T1.5
- T3
Q23 | The minimum number of theoretical plates is required for achieving a given separation in distillation column with
- No reflux
- Total reflux
- Zero reflux ratio
- Minimum reflux ratio
Q24 | For which of the following unit operations, Lewis number is of significance?
- Adsorption
- Binary distillation
- Gas absorption
- Humidification
Q25 | Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the
- Latent heat
- Humid heat
- Specific heat
- Sensible heat