What typically constitutes a buffer solution?

A buffer solution is designed to resist changes in pH when small amounts of acid or base are added. This is typically achieved using a weak acid and its conjugate base. In this setup, the weak acid can neutralize added bases, while the conjugate base can neutralize added acids, maintaining the overall pH of the solution relatively stable.

For instance, if a weak acid like acetic acid is used, it donates protons (H⁺) when a base is added, which helps to minimize the increase in pH. Conversely, when an acid is added to the buffer, the conjugate base (from the weak acid) can react with the additional protons, preventing a significant drop in pH.

This capacity to maintain pH balance is essential in biological and chemical processes where pH changes can create an unfavorable environment for reactions or biological functions. Other combinations, such as strong acids with bases or saturated salt solutions, do not provide this buffering capacity; they either fully dissociate in solution or do not adequately resist changes in pH.