What does a buffer solution do?

A buffer solution is designed to maintain a relatively constant pH when small amounts of an acid or base are added. This is achieved by the presence of a weak acid and its conjugate base (or vice versa) in equilibrium. When an acid is added to the buffer solution, the weak base component of the buffer can react with the added hydrogen ions to minimize the change in pH. Conversely, if a base is added, the weak acid in the solution can donate protons to counteract the increase in pH.

This capacity to resist changes in pH is crucial in biological systems and various chemical applications, where maintaining a stable pH is essential for optimal function.

In contrast, changing the pH drastically or completely neutralizing acids and bases are not characteristics of buffer solutions; these functions generally result in significant changes to the solution's pH rather than stability. Additionally, claiming that a buffer has a constant pH regardless of acid or base addition is misleading because while buffers do resist changes, they still can experience pH alterations if excess amounts of acid or base are added, surpassing the buffer's capacity.