High pressure at the bottom of a distillation tower handling heat sensitive materials results in
A. Thermal decomposition of bottoms
B. Increased relative volatility
C. Erosion of the tower
D. Very efficient operation
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In a counter-current extractor, as the axial mixing increases, the extraction efficiency
A. Increases
B. Decreases
C. Remains unchanged
D. Depends on the pressure of the system
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Mass transfer co-efficient of liquid is
A. Affected more by temperature than that for gases
B. Affected much less by temperature than that for gases
C. Not affected by the temperature
D. None of these
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The rate of mass transfer is not dependent upon the
A. Degree of dispersion of one fluid in the other
B. Interfacial surface exposed between the phases
C. Both A & B
D. None of these
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Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number.
A. Sherwood
B. Schmidt
C. Peclet
D. Stanton
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Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the __________ number.
A. Schmidt
B. Sherwood
C. Peclet
D. Stanton
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The expression, x ( 1 − y ) y ( 1 − x ) is for
A. Absorption factor
B. Relative volatility
C. Selectivity
D. Murphree efficiency
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The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and m = slope of the equilibrium line)
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When both the fluids flow concurrently in an absorber, the slope of the operating line is
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Smoke is an example of
A. Solid dispersed in liquid
B. Solid dispersed in gas
C. Liquid dispersed in gas
D. Gas dispersed in liquid
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The value of L/mG ratio for economical absorption operation ranges from
A. 0.5 to 0.8
B. 0.8 to 1.2
C. 1.25 to 2.0
D. 2.5 to 3.5
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Swenson-Walker crystalliser is a __________ unit
A. Continuous
B. Batch
C. Semi-batch
D. Cooling (adiabatic)-cum-evaporation
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Steam distillation is used to
A. Reduce the number of plates
B. Avoid thermal decomposition of a component
C. Increase the efficiency of separation
D. Increase the total pressure of distillation
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For water-ethanol system, the minimum reflux ratio
A. Is computed from the slope of the upper operating line that is tangent to the equilibrium curve
B. Is computed from the intercept of the operating line
C. Cannot be computed
D. Is the optimum reflux ratio
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At what value of reflux ratio, number of theoretical plates in a distillation column is minimum?
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Fenske-Underwood equation used for calculating the minimum number of theoretical plates in distillation column is valid for
A. Constant molal overflow
B. Total reflux
C. Constant relative volatility
D. All of the above
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Steam distillation is used to separate
A. Azeotropes
B. High boiling substances from nonvolatile impurities
C. Heat sensitive materials
D. Mixtures of low relative volatility
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According to Chilton-Colburn analogy for mass transfer, N St . N Sc 3 2 is equal to
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The percentage humidity is less than the relative humidity only at __________ percent humidity.
A. Zero
B. Hundred
C. Both zero and hundred
D. None of these
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Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled
A. And humidified
B. And dehumidified with increase in wet bulb temperature
C. At the same relative humidity
D. And dehumidified with decrease in wet bulb temperature
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