Mass Transfer
Steady state equimolal counter diffusion occurs in case of

Binary phase distillation
Absorption
Liquid-liquid extraction
Leaching

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Mass Transfer
When the solvent dissolves very little of solute, then

Solvent of low latent heat of vaporisation should be used
Solvent of low freezing point should be used
Very small quantity of solvent is required
Large quantity of solvent is required to extract the solute

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