The pH of a solution can be kept constant by:

Explanation

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added to it. It consists of a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid). The buffer solution works by undergoing a reversible reaction that consumes or releases hydrogen ions (H+) to maintain a relatively constant pH. The buffer solution responds to the addition of acid or base by shifting the equilibrium of the weak acid-conjugate base pair, minimizing the change in pH.Buffer solutions are used where maintaining a constant pH is critical.