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Chemical Engineering :: Mass Transfer

  1. Agitator is provided in a crystalliser for

  2. A.
    avoiding deposition on cooler surfaces.
    B.
    formation of nuclei.
    C.
    crystal growth.
    D.
    all (a), (b) and (c).

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  3. __________ diffusion is used for separating the isotopes of methane.

  4. A.
    Thermal
    B.
    Pressure
    C.
    Concentration
    D.
    Force

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  5. Ordinary diffusion process is also called __________ diffusion.

  6. A.
    pressure
    B.
    thermal
    C.
    concentration
    D.
    forced.

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  7. Pick out the wrong statement.

  8. A.
    Different solids have different equilibrium moisture curves.
    B.
    Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column.
    C.
    Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
    D.
    Even a forced draft cooling tower can not cool water below the wet bulb temperature.

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  9. Pick out the wrong statement pertaining to the rotary dryer.

  10. A.
    Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12% of the inside diameter of shell.
    B.
    Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.05 to 0.15.
    C.
    Rotary dryer is suitable for drying sticky material.
    D.
    Recommended peripherial speed of a rotary drier is in the range of 10 to 30 metres/minute.

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  11. The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives

  12. A.
    low pressure drop and high hold up.
    B.
    high pressure drop and low hold up.
    C.
    low pressure drop and low hold up.
    D.
    high pressure drop and high hold up.

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  13. If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent.

  14. A.
    100
    B.
    > 100
    C.
    < 100
    D.
    none of these

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  15. 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

  16. A.
    25%
    B.
    50%
    C.
    70%
    D.
    90%

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  17. Raoult's law is applicable to the

  18. A.
    ideal solutions
    B.
    real solutions
    C.
    mixture of water and alcohol
    D.
    non-ideal gases

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  19. Weeping in a distillation column

  20. A.
    increases tray efficiency.
    B.
    provides large interfacial surface for mass transfer.
    C.
    results due to very high gas velocity.
    D.
    results due to very low gas velocity.

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