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Chemical Engineering :: Mass Transfer

  1. The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by

  2. A.
    increasing the gas film co-efficient.
    B.
    increasing the liquid film co-efficient.
    C.
    increasing the total pressure.
    D.
    decreasing the total pressure.

  3. Flooding results in

  4. A.
    high tray efficiency
    B.
    low tray efficiency
    C.
    high gas velocity
    D.
    good contact between the fluids

  5. For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because

  6. A.
    water has a high latent heat of evaporation.
    B.
    Lewis number is close to unity.
    C.
    they are always equal under all circumstances.
    D.
    solubility of the components of air in water is very small.

  7. In an operating distillation column, the

  8. A.
    vapors and liquids are at their dew point and bubble point respectively
    B.
    driving force for the liquid flow is its specific weight.
    C.
    driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.
    D.
    highest temperature is encountered at the top of the column.

  9. In a forced draft cooling tower, water is cooled from 95 to 80°F by exposure to air with a wet bulb temperature of 70°F. In this case, the

  10. A.
    range is 15°F.
    B.
    approach is 10°F.
    C.
    both (a) & (b).
    D.
    neither (a) nor (b).

  11. The diffusivity (D) in a binary gas mixture is related to the temperature (T) as

  12. A.
    DT
    B.
    DT0.5
    C.
    DT1.5
    D.
    DT2

  13. For which of the following unit operations, Lewis number is of significance ?

  14. A.
    Adsorption
    B.
    Binary distillation
    C.
    Gas absorption
    D.
    Humidification

  15. Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches.

  16. A.
    5
    B.
    30
    C.
    60
    D.
    100

  17. If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement.

  18. A.
    a1 = a2
    B.
    a1 = 2a2
    C.
    a1 = 0.5 a2
    D.
    none of these

  19. The dimension of diffusivity is same as that of the

  20. A.
    density
    B.
    molal concentration
    C.
    kinematic viscosity
    D.
    velocity head