Mass Transfer
A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state,

The top and bottom compositions correspond to the maximum enrichment available
Composition of vapors and that of liquid do not vary throughout the column
The top and bottom compositions are unchanged with and without total reflux
Reboiler load and condenser load are minimum

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Mass Transfer
As the reflux ratio in a distillation coloumn is increased from the minimum, the

Slope of the operating line in stripping section decreases
Total cost first decreases and then increases
Number of plates decreases very slowly first and then more and more rapidly
Liquid flow increases while the vapor flow decreases for a system

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Mass Transfer
Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m² and the solvent flow, rate is 400 moles of S/m². hr. The equilibrium data is represented by Y = 3X² , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is

0.9
0.5
0.25
0.7

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Mass Transfer
In case of a desorber (stripper), the

Temperature always increases
Operating line always lies below the equilibrium curve
Temperature remains unaffected
Operating line always lies above the equilibrium curve

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Mass Transfer
In a counter-current liquid extractor

Both liquids can have any desired flow rate
Both liquids flow at fixed rate
Liquid's flow rate depends upon the temperature and pressure
Only one of the liquids may be pumped at any desired rate

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