Chemistry – Acids, bases and salts - Preparation of salts | e-Consult

Preparation: A solution of an alkali (e.g., sodium hydroxide, NaOH) is reacted with a solution of a metal salt (e.g., zinc chloride, ZnCl₂). The reaction produces a soluble salt and a precipitate. The balanced equation for the reaction between sodium hydroxide and zinc chloride is:

Separation: The precipitate (e.g., zinc hydroxide, Zn(OH)₂) is separated from the solution by filtration. This is done using a Buchner funnel and filter paper. The filtrate contains the desired soluble salt (e.g., sodium chloride, NaCl).

Purification: The filtrate is then evaporated to dryness. This leaves the solid salt, which may be impure. The salt can be further purified by recrystallization. This involves dissolving the impure salt in a minimum amount of hot water, filtering the hot solution to remove any insoluble impurities, and then allowing the solution to cool slowly. As the solution cools, the pure salt crystallizes out, leaving the impurities behind in the solution. The crystals are then filtered, washed with cold water, and dried.