Question

You are given a mixture of sand, common salt and naphthalene (Fig. a). The Fig. b depicts various steps used to separate the components of this mixture. Identify and write down the correct sequence of separation techniques.

Answer 1

The correct sequence of separation techniques is

Step 1 – Sublimation: Heat the mixture so that naphthalene changes directly into vapour. The vapour is cooled to obtain solid naphthalene, while sand and common salt remain behind.

Step 2 – Filtration: Add water to the remaining mixture of sand and common salt. The common salt dissolves in water, but the sand remains insoluble. Filter the mixture to separate the sand as the residue, while the salt solution passes through as the filtrate.

Step 3 – Evaporation: Heat the salt solution to evaporate the water. Once the water has evaporated, common salt is left behind as the solid residue.

Complete sequence:

Sublimation (image 1) → Filtration (after dissolution) (image 3) →Evaporation (image 2)