Question

Naphthalene and sodium chloride

• Give the principle involved in the separation of the mixture
• Give the technique of separation of the mixture.

Answer 1

By Sublimation

Principle: Based on the difference in sublimable and non- sublimable nature of solids.
Sublimation: It is the process of conversion of a solid directly into vapour and back to solid without passing through the liquid state.
Sublimable solids thus turn directly into vapour on heating and back to pure solid on cooling the vapours. The non- sublimable solid in the mixture thus remains behind.

The technique of Separation – The mixture of the sublimable and non-sublimable solids are heated in an evaporating dish covered with a funnel plugged at one end with cotton. Sublimable solid on heating sublimes and the vapours condense and collect in the pure form on the inner side of the funnel, from where the sublimable solid is scrapped off. Non-sublimable solid remains behind in the evaporating dish.