Why is it not possible to obtain pure ethanol by fractional distillation ? What general name is given to binary mixture which show deviation from Raoult's law and whose omponents cannot be separted by fractional distillation. How many types of such mixture are there?

Explanation

Pure ethanol cannot be obtained by fractional distillation because when the mixture attains a composition of `95.6%` alcohol and `4.4%` water, it becomes an azeotropic mixture. In general, such mixture are called 'azeotropes'. There are two types of such mixtures as follows :
(i) Minimum boiling azeotropes formed from non-ideal solutions `+ve` deviations.
(ii) Minimum boiling azeotropes formed from non-ideal solutions showing `-ve` deviations.