Provide an example of the common ion effect on the stability of complexes.

The common ion effect can affect the stability of complexes, as seen in the formation of silver chloride.

When silver ions (Ag+) and chloride ions (Cl-) combine, they form a complex ion called silver chloride (AgCl). This reaction is reversible, meaning that the silver chloride can dissociate back into its component ions. However, the presence of a common ion, such as chloride ions in the solution, can affect the equilibrium of the reaction.

If more chloride ions are added to the solution, the equilibrium will shift towards the dissociation of the silver chloride complex. This is because the common ion (chloride) reduces the concentration of the silver ions, making it less likely for them to combine with the chloride ions to form the complex. As a result, the stability of the silver chloride complex decreases.

On the other hand, if the concentration of silver ions is increased, the equilibrium will shift towards the formation of more silver chloride complex. This is because the increased concentration of silver ions makes it more likely for them to combine with the chloride ions to form the complex. As a result, the stability of the silver chloride complex increases.

Overall, the common ion effect can have a significant impact on the stability of complexes. By understanding this effect, scientists can manipulate the equilibrium of reactions to favour the formation or dissociation of certain complexes.