In a buffer solution, what happens when small amounts of acid are added?

In a buffer solution, the primary purpose is to resist changes in pH when small amounts of acid or base are introduced. When an acid is added to a buffer, the weak acid-base pair present in the solution reacts with the added hydrogen ions (H⁺) from the acid. The weak base component of the buffer will combine with the excess H⁺ ions to form more of the weak acid, thus minimizing the increase in hydrogen ion concentration.

This ability of a buffer to maintain its pH is due to the equilibrium established between the weak acid and its conjugate base. When a small amount of acid is added, the buffer system effectively absorbs the added H⁺ ions, thereby stabilizing the pH. The overall change in pH is relatively minor, demonstrating the effectiveness of the buffer’s components in resisting dramatic pH shifts. This characteristic makes buffer solutions invaluable in biological and chemical systems where maintaining a consistent pH is crucial.