Mass Transfer
An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is

0.122
0.152
0.048
0.079

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Mass Transfer
Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)

Increases pressure drop, increases surface area
Decreases pressure drop, decreases surface area
Increases pressure drop, decreases surface area
Decreases pressure drop, increases surface area

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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 At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped).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
The top and bottom compositions correspond to the maximum enrichment available
The top and bottom compositions are unchanged with and without total reflux
Reboiler load and condenser load are minimum

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