Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty?
A. Grid tray tower
B. Perforated tray tower
C. Wetted wall tower
D. Bubble cap tower
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Heat sensitive materials with very high latent heat of vaporisation may be economically separated using
A. Liquid extraction
B. Distillation
C. Evaporation
D. Absorption
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The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.
A. Exponential
B. Parabolic
C. Linear
D. Cubic
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Leaching of coffee from coffee beans is done by
A. Hot water
B. Hexane
C. Lime water
D. Dilute H2 SO4 (hot)
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The Hatta number is important in
A. Multicomponent distillation
B. Binary distillation
C. Gas absorption without chemical reaction
D. Gas absorption with chemical reaction
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Relative humidity is the ratio of the
A. Partial pressure of the vapour to the vapour pressure of the liquid at room temperature
B. Partial pressure of the vapour to the vapour pressure of the liquid at gas temperature
C. Actual humidity to saturation humidity
D. None of these
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Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele's method?
A. Partial condenser
B. Total condenser
C. Reboiler
D. Both B and C
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Absorption factor method is used to calculate the number of ideal stages, when
A. Operating line lies above the equilibrium line
B. Operating line lies below the equilibrium line
C. Both operating and equilibrium lines are parallel
D. Pressure drop in the column is very high
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Berl saddle made of carbon cannot be used for
A. Alkalis
B. SO2
C. H2 SO4
D. Oxidising atmosphere
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During constant rate period, the rate of drying decreases with the
A. Decrease in air temperature
B. Increase in air humidity
C. Both A & B
D. Neither A nor B
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At 750°K and 1 atm, the approximate value of Schmidt number for air is
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The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives
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
Select an option to see the answer and solution.
During constant rate drying period, vaporisation rate per unit drying surface area
A. Decreases with time
B. Increases with time
C. Does not change with time
D. Does not affect the moisture content of the wet solid
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During the constant rate period of drying of a solid,
A. Increased air humidity decreases the rate of drying
B. Increasing the air temperature decreases the drying rate
C. Surface evaporation of unbound moisture occurs
D. None of these
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Inside the distillation column, the
A. Driving force for the vapour flow is the pressure drop
B. Liquids are not always at their bubble points
C. Pressure increases gradually from bottom to the top of the column
D. None of these
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Pick out the wrong statement.
A. Critical moisture content is not a property of the material itself
B. A sharp increase in pressure drop gives an indication of the flooding in a distillation column
C. Separation of components is not possible in liquid extraction, if selectivity is unity
D. Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum
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Plate efficiency in a distillation column is reduced due to the __________ of liquid.
A. Entrainment
B. Foaming
C. Weeping & dumping
D. All of the above
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With increase in temperature, the rate of leaching increases, because the
A. Diffusivity of solute increases
B. Viscosity of solvent decreases
C. Thermal conductivity of solute increases
D. None of these
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Stage efficiency in a leaching process depends on the
A. Time of contact between the solid and the solution
B. Rate of diffusion of the solute through the solid and into the liquid
C. Both A & B
D. Vapour pressure of the solution
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In a distillation operation, what is the effect of the temperature of the reflux stream (given below) on the condenser and reboiler loads? Reflux conditions: (i) Reflux stream is completely liquid and is at its bubble point. (ii) Reflux stream is below its bubble point.
A. Condenser and reboiler loads are the same in both the cases
B. Reboiler load is the same in both the cases but condenser load is higher in case (ii)
C. Condenser load is the same in both the cases but reboiler load is higher in case (ii)
D. Both condensor and reboiler loads are higher in case (ii) as compared to case (i)
Select an option to see the answer and solution.