Chemical Engineering Mass Transfer Objective Questions - Set 08

Practice Test: Question Set - 08

1. Which of the following is the correct ternary diagram for liquid-liquid extraction system comprising of one pair partly soluble (e.g. water-benzene-acetic acid in which A - diluent, B - solvent and C - solute)?
2. Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations.
    (A) Sherwood number in mass transfer is analogous to Nusselt number in heat transfer
    (B) Prandtl number in heat transfer is analogous to Schmidt number in mass transfer
    (C) Reynolds number in mass transfer is analogous to Grashoff number in heat transfer
    (D) Reynolds number remains the same in both heat and mass transfer
3. Plate efficiency in a distillation column is reduced due to the __________ of liquid.
    (A) Entrainment
    (B) Foaming
    (C) Weeping & dumping
    (D) All (a), (b) & (c)
4. Pick out the wrong statement.
    (A) Mass transfer co-efficient does not account for gas-liquid diffusion
    (B) Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation
    (C) Contacting cold vapor-gas mixture with hot liquid exemplifies humidification process
    (D) Contacting cold liquid with warm vapor-gas mixture exemplifies dehumidification process
5. Blowdown in a cooling tower
    (A) Means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities
    (B) Increases the scale forming tendencies of water
    (C) Is undesirable
    (D) All (a), (b) & (c)
6. Pick out the wrong statement.
    (A) In solvent extraction, the distribution co-efficient should be as large as possible for solvent economy
    (B) With increase in pressure, the solubility of gases in solvent increases at a fixed temperature
    (C) Decrease in Murphree plate efficiency is an indication of entrainment in distillation column
    (D) The capacity of a distillation column is maximum at total reflux
7. Rayleigh's equation applies to __________ distillation.
    (A) Continuous
    (B) Steam
    (C) Differential
    (D) Flash
8. In extraction, as the temperature increases, the area of heterogeneity (area covered by binodal curve)
    (A) Decreases
    (B) Increases
    (C) Remains unchanged
    (D) None of these
9. In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in
    (A) Reducing the axial mixing
    (B) Increasing the rate of extraction
    (C) Maintaining the concentration difference between the two phases
    (D) All 'a', 'b' & 'c'
10. The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2/m3)
    (A) 500
    (B) 1200
    (C) 900
    (D) 800
11. The slope of 9-line is determined by the
    (A) Reflux ratio
    (B) Plate efficiency to be achieved
    (C) Thermal condition of the feed
    (D) Relative volatility
12. For a binary mixture with low relative volatility,
    (A) Use steam distillation
    (B) Use molecular distillation
    (C) Use high pressure distillation
    (D) An azeotrope may be formed during distillation
13. Freundlich equation applies to the adsorption of solute from
    (A) Dilute solutions, over a small concentration range
    (B) Gaseous solutions at high pressure
    (C) Concentrated solutions
    (D) None of these
14. Pick out the wrong statement pertaining to the cooling towers.
    (A) In case of induced draft cooling tower, the fan is placed at the top of the tower
    (B) Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air
    (C) A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low
    (D) Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature
15. The Hatta number is important in
    (A) Multi-component distillation
    (B) Binary distillation
    (C) Gas absorption without chemical reaction
    (D) Gas absorption with chemical reaction
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