Mass Transfer
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.

Condenser and reboiler loads are the same in both the cases
Reboiler load is the same in both the cases but condenser load is higher in case (ii)
Both condensor and reboiler loads are higher in case (ii) as compared to case (i)
Condenser load is the same in both the cases but reboiler load is higher in case (ii)

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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 At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped).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,

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

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Mass Transfer
Plate efficiency

Increases due to liquid entrainment
Is a function of the mass transfer between liquid and vapour
Increases due to foaming
Increases due to weeping and dumping of liquid

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