Mass Transfer
Relative volatility varies with the concentration of component for an ideal solution. The relative volatity of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when

Only liquid phase obeys Dalton's law
Only vapor phase follows Raoult's law
Liquid phase obeys Dalton's law and vapor phase obeys Raoult's law
Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law

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

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Mass Transfer
In case of absorption with exothermic reaction, for fluids having

Pr = Sc ; there won
Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same
Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence
Both A & B

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