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 carbonate (e.g., potassium carbonate, K₂CO₃). The reaction produces a soluble salt, water, and carbon dioxide gas. The balanced equation for the reaction between sodium hydroxide and potassium carbonate is:

Separation: The solution is filtered to remove any insoluble impurities. The filtrate contains the desired soluble salt (e.g., sodium carbonate, Na₂CO₃). Carbon dioxide gas is evolved during the reaction, which can be observed as bubbles.

Purification: The filtrate is 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.