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

The solution or mixture having same composition in liquid as well as in vapour phase and boils at a constant temperature is known as azeotropes. Due to constant composition it can't be spearted by fractional distillation. There are two types of azeotropes
(i) Minimum boiling azeotropes Solution which show large positive adviation from Raoult's law from minimum boiling azeotropes at a specific composition. e.g., ethanol - water mixture
(ii) Maximum boiling azeotropes Solution which show large negative deviation from Raoult's law from maximum boiling azeotropes. e.g., solution having composition 68% `HNP_(3) and 32%` water by mass