What is meant by buffer capacity?

Buffer capacity refers to the ability of a buffer solution to resist changes in pH when an acid or base is added. This property is crucial in many chemical and biological processes where maintaining a stable pH is essential. A buffer solution typically consists of a weak acid and its conjugate base (or a weak base and its conjugate acid). When an acid is added to the solution, the conjugate base can neutralize it, and when a base is added, the weak acid can react with it, thereby minimizing changes in pH.

The other options do not accurately capture the essence of buffer capacity. For instance, while some may mistakenly consider the ability of a solution to change pH quickly as a measure of its effectiveness, this actually highlights a lack of buffer capacity. Additionally, the total volume a buffer solution can hold relates more to the physical parameters of the solution rather than its chemical functionality. Finally, the strength of a buffer solution could refer to its concentration or how effectively it can maintain pH, but it does not fully encompass the nuanced concept of buffer capacity, which is specifically about resistance to pH change. Thus, the definition emphasizing resistance to pH changes encapsulates the fundamental role buffer solutions play in chemical stability.