See explanation below.
Work Step by Step
The common ion effect is responsible for the decrease in the solubility of an ionic precipitate when a soluble compound having one of the ions of the precipitate is added to the solution in equilibrium with the precipitate. The presence of an ion in common between two solutes will cause any equilibrium involving either of them to shift as per the Le Chatelier’s principle. For example, addition of NaF to a solution of HF will cause equilibrium to shift to the left. HF (aq) + H2O (l) H3O+ (aq) + F-(aq)