Mass Transfer
At minimum reflux ratio for a given separation

Minimum number of the theoretical plates is required
Number of plates is zero
Number of plates is infinity
Separation is most efficient

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

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

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