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Chemical Engineering :: Mass Transfer

  1. 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)

  2. A.
    500
    B.
    1200
    C.
    900
    D.
    800

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  3. Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysterisis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption.

  4. A.
    lower than
    B.
    higher than
    C.
    same as
    D.
    either same or higher than

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  5. Experimental determination of __________ is done by wetted wall column method.

  6. A.
    diffusion co-efficient
    B.
    mass transfer co-efficient
    C.
    NTU
    D.
    none of these

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  7. Pick out the wrong statement:

  8. A.
    Absorption factor is constant, when the equilibrium and operating lines are straight.
    B.
    In case of a stripper, the equilibrium curve is always below the operating line.
    C.
    In case of an absorber, the operating line is always above the equilibrium curve.
    D.
    In the absorption of low solubility gases, the liquid film is the controlling resistance.

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  9. In liquid extraction, if the selectivity is unity, then

  10. A.
    separation of the constituents is the most effective.
    B.
    no separation will occur.
    C.
    amount of solvent required will be minimum.
    D.
    solvent flow rate should be very low.

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  11. Paper industry employs __________ driers.

  12. A.
    cylinder
    B.
    rotary
    C.
    spray
    D.
    fluidised bed

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  13. Which of the following has the same dimension as mass diffusivity ?

  14. A.
    Momentum flux
    B.
    Kinematic viscosity
    C.
    Thermal diffusivity
    D.
    Both (b) and (c)

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  15. Pick out the wrong statement pertaining to the cooling towers.

  16. 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.

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  17. Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 x 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is

  18. A.
    5.6 x 10-4
    B.
    8.5 x 10-4
    C.
    5.6 x 10-3
    D.
    8.5 x 10-3

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  19. Leaching of coarse solid lumps is also termed as

  20. A.
    decoction
    B.
    dissolution
    C.
    percolation
    D.
    agitation and settling

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