Question

Define azeotropes. What type of azeotropes is formed by a positive deviation from Raoult's law? Give an example.

Answer 1

Hint- Azeotropes are the special kind of solution. They are binary solutions that means they are the mixture of two solutions. Those solutions are having some properties similar to each other with respect to some of the physical properties.

Complete step by step solution:
> Definition: Azeotropes are the binary mixture of the solution of the same composition in its both phases (liquid phase and vapour phase) and that have constant boiling points during the whole distillation process.
> Azeotropes are constant boiling mixtures which have boiling points either lower or higher then both the constituents components .
> Azeotropes formed by a positive deviation from the Raoult’s law at specific composition are minimum-boiling azeotropes.
Example-A mixture of ethanol and water in which ethanol is 95% by volume. This azeotropes mixture is minimum-boiling azeotropes.

Notes- Raoult’s law says that the boiling and freezing points of an ideal solution are respectively elevated and depressed relative to that of pure solvent, and this amount of elevation or depression is proportional to the mole fraction of the solute.
Also, in some other words Raoult’s law states that in a solution, the pressure of a component at a given temperature is equal to the multiplication of the mole fraction of that component in the solution and vapour pressure of that component in the pure state.
For the Positive deviation from the Raoult’s law to occur the vapour pressure of the component should be greater than what is expected in the Raoult’s law.