What characterizes a buffer solution?

A buffer solution is characterized by its ability to resist changes in pH when either acids or bases are added. This property arises from the presence of a weak acid and its conjugate base (or vice versa) in the solution. When a small amount of an acid or base is added, the buffer components react with the added species to minimize any change in pH.

Buffers do not require a specific pH level of 7; their pH can be above or below this value depending on the nature of the weak acid and its conjugate base. Additionally, buffers are not composed solely of strong acids or bases, as strong acids and bases fully dissociate in water and do not provide the necessary equilibrium that buffers rely on to maintain pH stability. Therefore, the ability to resist changes in pH is the defining characteristic of a buffer solution.