Question

Explain how, impure copper sulphate can be purified by crystallisation.

Answer 1

Impure copper sulphate can be purified by crystallization. Crystallization is a chemical solid–liquid separation technique in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.

Impure copper sulphate can be dissolved in minimum amount of water to prepare copper sulphate solution. It is then filtered to remove insoluble impurities. Now, copper sulphate solution is heated gently on a water bath to evaporate water and obtain a saturated solution. Heating should be stopped when all the water evaporates. The saturated solution of copper sulphate is then allowed to cool slowly. Crystals of pure copper sulphate are formed leaving behind impurities.