You are given an impure sample of sodium chloride containing impurity of some chalk. How will you purify it ?

Explanation

The impure sample of common salt containing some chalk impurity represents a heterogeneous mixture. In order to purify the sample or to recover common salt from it, dissolve about 5 g of the sample in minimum volume of water in a beaker. Stir occasionally with a glass rod. Filter the solution formed through funnel as discussed earlier. The chalk impurity will be left on the filter paper. The filtrate will be an aqueous solution of sodium chloride. Transfer the solution in a china dish. Concentrate by heating so that the volume of the solution becomes nearly half. The solution will be saturated. Place the china dish over a beaker full of water and allow to remain undisturbed for sometime. Pure crystals of sodium chloride will appear in the dish. They can be separated by using filtration technique as discussed earlier.