Mass Transfer
Fenske's equation for determining the minimum number of theoretical stages in distillation column holds good, when the

Mixture (to be separated) shows positive deviation from ideality
Relative volatility is reasonably constant
Mixture (to be separated) shows negative deviation from ideality
Multicomponent distillation is involved

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Mass Transfer
The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.)

Kc = Kp = Km
Kc = Kp/RT = Km . RT/P
None of these
Kc = Kp . RT = Km . RT/p

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