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This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on Mass Transfer Set 11
Q1 | Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2 . hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is
- 25%
- 50%
- 70%
- 90%
Q2 | Mass transfer co-efficient is directly proportional to DAB 0.5, according to __________ theory.
- Penetration
- Surface renewal
- Film
- None of these
Q3 | Which of the following gas-liquid contacting devices incurs the least pressure drop for aparticular duty?
- Grid tray tower
- Perforated tray tower
- Wetted wall tower
- Bubble cap tower
Q4 | For experimental determination of mass transfer co-efficient by wetted wall tower, themass transfer area is
- Calculated
- Unknown
- Known
- Not required
Q5 | With decrease in the throughput (compared with the design capacity) for a bubble capdistillation column, its efficiency
- Increases
- Decreases
- Remain same
- May increase or decrease; depends on individual design
Q6 | Diameter to height ratio for a raschig ring is
- 1
- 0.5
- 2
- 8
Q7 | Which of the following operations does not involve leaching?
- Dissolving gold from ores
- Dissolving pharmaceutical products from bark or roots
- Dissolving sugar from the cells of the beet
- Removing nicotine from its water solution by kerosene
Q8 | Flooding in a distillation column is detected by a sharp
- Increase in Murphree plate efficiency
- Decrease in pressure drop
- Decrease in liquid hold up in the column
- Increase in pressure drop
Q9 | In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction,
- Inversely
- Linearly
- Exponentially
- None of these
Q10 | With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system).
- Increases
- Decreases
- Remain unaffected
- Increases Linearly
Q11 | Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if
- Mass transfer is accompanied by reaction
- Diffusion of A is in stagnant medium B
- Molecular mean free path is high
- There is equimolar counter diffusion
Q12 | Absorption accompanied by heat evolution results in
- Increased capacity of the absorber
- Increase in equilibrium solubility
- Decrease in equilibrium solubility
- None of these
Q13 | The solvent used in liquid extraction should not have high latent heat of vaporisation, because
- The pressure drop and hence the pumping cost will be very high
- It cannot be recovered by distillation
- Its recovery cost by distillation may be prohibitively high
- It will decompose while recovering by distillation
Q14 | Mass transfer co-efficient varies as DAB0.5, according to the __________ theory.
- Film
- Surface renewal
- Penetration
- None of these
Q15 | The suitable evaporator for concentration of foaming liquids is a __________ evaporator.
- Long tube
- Short tube
- Vacuum
- Falling film
Q16 | In stripping section of continuous distillation column, the
- Liquid is stripped of high boiler
- Liquid is enriched with high boiler
- Vapour is stripped of low boiler
- None of these
Q17 | An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)
- Less number of trays are required
- Composition of the residue remains unchanged
- More number of trays are required but the residue composition remains unchanged
- More number of trays are required and the residue composition is more dilute in methanol
Q18 | The Schmidt number which is defined as, ?/? D, is the ratio of the
- Momentum diffusivity to the mass diffusivity
- Thermal diffusivity to the mass diffusivity
- Momentum diffusivity to the thermal diffusivity
- None of these
Q19 | NSc/NPr is called the
- Psychrometric ratio
- Lewis number
- Sherwood number
- Stanton number
Q20 | At constant pressure, with increase of temperature, the dew point will
- Increase
- Decrease
- Remain unchanged
- Increase/decrease; depends on the temperature
Q21 | Pick out the correct statement.
- Dialysis process is used for the production of fresh water from brine
- Electrodialysis is used in the manufacture of NaOH
- Electrodialysis is used for the refining/purification of petrol
- Both (B) and (C)
Q22 | The percentage humidity is less than the relative humidity only at __________ percent humidity.
- Zero
- Hundred
- Both zero and hundred
- None of these
Q23 | 'ADDUCTS' and 'CLATHRATES' are used in case of
- Extractive distillation
- Crystallisation
- Absorption
- None of these
Q24 | __________ is concerned with the adsorption equilibria.
- Fick's law
- Gibb's equation
- Freundlich equation
- None of these
Q25 | In most of the vacuum crystalliser, vacuum is generally produced by means of a
- Suction pump
- Compressed air jet
- Steam jet ejector with a barometric condenser
- None of these