Question

Pure water boils at nearly $373K$ and pure nitric acid at nearly $359K$. The azeotropic mixture of water and nitric acid boils at nearly $395K$.
On fractional distillation of the above azeotropic mixture:

• A. Pure nitric acid will distill first.
• B. Pure water will distill first.
• C. Both of them will distill over the same composition as in the mixture.
• D. Composition of nitric acid in the liquid mixture increases as the distillation progresses.

Answer 1

The correct option is C Both of them will distill over the same composition as in the mixture

Azeotropic mixtures are constant boiling mixtures. Fractional distillation works on the principle of difference in boiling points.
Since, an azeotropic mixture boils at a constant temperature so, both the components cannot be seperated by fractional distillation
During boiling, composition remains constant in liquid phase as well as the vapour phase.
So (c) is correct.