Question

How does azeotrope behavior influence the ability of distillation to separate a liquid mixture?

Answer 1

An azeotrope is otherwise known as constant boiling point mixture. It is a blend of two or more liquids whose proportions cannot be altered or changed by simple distillation. The vapours coming out from the boiling of azeotropes contain the same proportions of constituents as the unboiled mixture.

Each azeotrope has a characteristic boiling point. Different types of azeotropes are there. One is positive azeotrops. In this the boiling point of an azeotrope is either less than the boiling point temperatures of any of its constituents. Greater than the boiling point of any of its constituents is called negative azeotrope.

If two solvents can form a positive azeotrope, then distillation of any mixture of those constituents will result in the distillate being closer in composition to the azeotrope than the starting mixture.

If two solvents can form a negative azeotrope, then distillation of any mixture of those constituents will result in the residue being closer in composition to the azeotrope than the original mixture.

So because of this type of character, it is difficult to separate by simple distillation. It can be separated by fractional distillation method.