Which property of a buffer solution allows it to stabilize pH?

The ability of a buffer solution to stabilize pH is primarily due to its capacity to neutralize both acids and bases. Buffers are typically made up of a weak acid and its conjugate base, or a weak base and its conjugate acid. When an external acid (H⁺ ions) or base (OH⁻ ions) is added to the solution, the weak acid or base present in the buffer reacts with it, which helps to minimize any significant changes in pH.

For example, if an acid is added to a buffer, the conjugate base in the buffer will react with the added hydrogen ions, reducing their impact on the pH. Conversely, if a base is introduced, the weak acid in the buffer can donate hydrogen ions to counteract the increase in pH. This dynamic equilibrium allows buffer solutions to maintain a relatively constant pH even when small amounts of strong acids or bases are added.

While the acidity of the buffer, its concentration, and temperature can influence its overall effectiveness, it is the neutralization capacity—how well it can react with added acids and bases—that is the key property that defines its ability to stabilize pH.