Question

Common salt can be purified by a process of:
A. crystallization
B. homogenization
C. boiling
D. distillation

Answer 1

Hint: Common salt is the salt which is used mostly in household food preparations. The chemical composition of common salt is sodium chloride. It is a white crystalline solid.

Complete step by step answer:
The common salt is obtained from sea water. When sea water was confined in shallow pits the natural evaporation of the sea water by sunlight into vapor leaves behind a residue. This residue was then purified by crystallization to obtain common salt in pure form.

Crystallization. It is a process of purification of a pure compound from a mixture. For this the compound is dissolved in a solvent or solvent mixture by heating. The mixture is concentrated by evaporation of some solvent. The solvent upon cooling leads to precipitation of crystals of the pure compound. These are then filtered and dried to obtain the final compounds.

Homogenization. Homogenization is a process of mixing two insoluble liquids into a mixture. This is actually achieved by distributing one liquid into another liquid in the form of small particles.

Boiling. Boiling is a technique used for purification of water. It is used to kill various harmful microorganisms present in water. Boiling water also removes the calcium and magnesium salts by precipitation of salts. Actually the calcium hydrogen carbonate and magnesium hydrogen carbonate present in water are responsible for the hardness of water which decomposes on boiling and precipitates as calcium carbonate and magnesium carbonate.

Distillation. It is the process of separating two liquids from a mixture. The liquids must have different boiling points. When heated at different temperatures they get distilled off from the mixture and lead to each of the components in pure form.


Hence option A is the correct answer.

Note:
Salts are ionic compounds which dissociate in solution and conduct electricity. There are several other purification techniques like sublimation, extraction and chromatography. Distillation purification is of three types like fractional, vacuum and steam distillation.