Question

Can we separate the compounds of azeotropic mixture by fractional distillation? Explain.

Answer 1

Hint: An azeotrope is a liquid mixture which has a constant boiling point and whose vapor has the same composition as that of the liquid. If a liquid has the same composition in both its liquid as well as vapor phase, it cannot be separated by the process of fractional distillation.

Complete step by step answer:
In the process of a fractional distillation of any liquid mixture, the liquids with different boiling points are heated over a wide range of temperature. The one whose boiling point is lower than the others will boil earlier and would rise in the vapor form and get separated from the mixture. Then the same process will be employed by the second liquid then the third and so on. But any liquid mixture that boils at the same temperature and the composition of the mixture is same in both its liquid phase as well as vapor phase cannot be separated with the help of fractional distillation. This liquid mixture having the same composition in its liquid as well as vapor phase is known as the azeotropic mixture or constant boiling mixture. The examples of such mixtures are: chlorobenzene and bromobenzene, water and ethanol, etc.
So conclusively we can say that we can not separate an azeotropic mixture by fractional distillation.

Note:
We should remember that any liquid mixture which boils at a constant temperature cannot be separated by any of the heating techniques as their boiling points become the same. The general principle behind distillation is the difference in the boiling points of the individual components of the liquid mixture.