Question

what is a common ion effect ? explain the effect for the solution containing CH3COOH and CH3COONa​

Answer 1

Common ion effect:

The common-ion effect refers to the decrease in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate. This behaviour is a consequence of Le Chatelier's principle for the equilibrium reaction of the ionic association/dissociation.

Explanation of effect:

The pH will increase.

CH3COONa is formed by the reaction of sodium hydroxide and acetic acid.

Acetic acid is a weak acid sodium hydroxide is strong base.

Thus, sodium acetate is basic in nature.

When sodium acetate added to aqueous solution of acetic acid which is acidic in nature, the concentration of H+ decreases.

So, there is increase in the pH of solution.

Answer 2

The effect in which when a weak acid or a weak base is added and contain same anions(ions), is called common ion effect.

Effect of common ion effect:-

CH3COONa is formed by the reaction of sodium hydroxide (strong base) and acetic acid ( weak acid). The sodium acetate is basic in nature. When sodium acetate added to aqueous solution of acetic acid the concentration of H+ion decreases.