Question

Azeotropic mixtures are:
(a)- Mixture of two solids
(b)- Those which boil at different temperature
(c)- Those which can be fractionally distilled
(d)- Constant boiling mixture

Answer 1

Hint An azeotropic mixture is also known as an azeotrope. Azeotropic mixtures are those in which two liquids are there in which composition is definite and the boiling point is like a pure liquid.

Complete answer:
When the solutions show positive deviation from Raoult’s law, at one of the intermediate compositions, then the total vapor pressure is the highest and the boiling point is the lowest and when the solutions show negative deviations from Raoult’s law, for one intermediate composition, then the vapor pressure is the lowest and the boiling point is the highest. The composition of the liquid and the vapor pressure is the same for the liquid pairs having such intermediates. This means that the liquid mixture having such composition, on vaporization and condensation there is no change in the composition i.e., the mixture distills as it is a pure liquid. Therefore, these are called an azeotropic mixture.
An azeotropic mixtures are one in which two liquids are there in which composition is definite and the boiling point is like a pure liquid and these are also known as a constant boiling mixture.
If there is a positive deviation then we get minimum boiling azeotropes and if there is a negative deviation then we get maximum boiling azeotropes.

Therefore, the correct answer is an option (d)- Constant boiling mixture.

Note: A mixture of water and ethanol is a minimum boiling azeotrope because the boiling point of the azeotrope is less than the boiling point of either of the pure components. A mixture of water and hydrogen chloride is a maximum boiling azeotrope; the boiling point of the azeotrope is more than the boiling point of either of the pure components.