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Chemical Engineering :: Mass Transfer

  1. For a distillation column operating at minimum reflux, the

  2. A.
    concentration of liquid and vapour leaving a plate will be same.
    B.
    reflux ratio will be maximum.
    C.
    number of plates required will be maximum.
    D.
    none of these.

  3. A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids))

  4. A.
    M(Xo - XF)
    B.
    M(Xo/XF)
    C.
    M ln(Xo/XF)
    D.
    MXo ln(Xo/XF)

  5. Flash distillation is suitable for the separation of components

  6. A.
    having very close boiling points.
    B.
    which form maximum boiling azeotrope.
    C.
    having very wide boiling points.
    D.
    which form minimum boiling azeotrope.

  7. In Mcabe-Thiele method, at infinite reflux ratio

  8. A.
    number of plates is maximum.
    B.
    overhead product is maximum.
    C.
    both the operating lines coincide with the diagram.
    D.
    none of these.

  9. Leaching rate is independent of the

  10. A.
    agitation
    B.
    temperature
    C.
    particle size
    D.
    none of these

  11. Use of packed towers for distillation is generally limited to the

  12. A.
    small sizes.
    B.
    multicomponent distillation.
    C.
    high pressure operation.
    D.
    vacuum distillation.

  13. Pick out the wrong statement.

  14. A.
    The binary diffusivity in liquids is of the order of 10-5 cm2 /sec.
    B.
    Molecular diffusion in solid is much faster than that in liquids.
    C.
    Particles movement from higher concentration to lower concentration takes place in diffusion process.
    D.
    According to Poiseuille's law, the permeability decreases with increase in temperature for flow of a gas through a given capillary.

  15. Which of the following decreases during evaporative cooling process with recirculated water supply ?

  16. A.
    Wet bulb temperature
    B.
    Relative humidity
    C.
    Partial pressure of vapour
    D.
    None of these

  17. Laboratory determination of the dif-fusivity of vapor is done by __________ method.

  18. A.
    wetted wall column
    B.
    Gilliland's
    C.
    Winkel mann's
    D.
    Wike's

  19. The minimum liquid rate to be used in an absorber corresponds to an operating line

  20. A.
    of slope = 1
    B.
    ofslope = 0.1
    C.
    tangential to the equilibrium curve
    D.
    none of these