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Chemical Engineering :: Mass Transfer

  1. At 750°K and 1 atm, the approximate value of Schmidt number for air is

  2. A.
    0.01
    B.
    0.1
    C.
    1
    D.
    10

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  3. Calculation of mass transfer co-efficient is mostly/normally done using __________ theory.

  4. A.
    surface renewal
    B.
    film
    C.
    penetration
    D.
    none of these.

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  5. The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if

  6. A.
    NSc = 1
    B.
    NSc = NPr = NLe
    C.
    NPr = NLe
    D.
    NSc = NLe

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  7. For the gas absorption, the height of a transfer unit, based on the gas phase is given by (G: superficial molar gas velocity, L: superficial molar liquid velocity, FG:mass transfer co-efficient, mols/m2 , a: in-terfacial area per unit volume of tower)

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  9. Which of the following is used for the concentration of rubber latex ?

  10. A.
    Agitated film evaporator
    B.
    Long tube vertical evaporator
    C.
    Short tube evaporator
    D.
    Calendria

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  11. As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages

  12. A.
    increase
    B.
    decrease
    C.
    remain unchanged
    D.
    can either increase or decrease, depends on the system

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  13. In triangular co-ordinates, the ternery composition point falls __________ of the triangle.

  14. A.
    in the corners
    B.
    inside
    C.
    on the sides
    D.
    none of these.

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  15. In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raf-finate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg)

  16. A.
    6.89
    B.
    8.89
    C.
    10
    D.
    8.25

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  17. Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)

  18. A.
    (De.t)1/2
    B.
    (De/t)1/2
    C.
    (4Det)1/2
    D.
    (4De/t)

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  19. Reboiler is considered as one theoretical plate, because

  20. A.
    of the assumption that vapour and liquid leaving the reboiler are in equilibrium.
    B.
    vapour is recycled to the column.
    C.
    reboiler itself contains one plate.
    D.
    none of these.

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