Why are weak acids and bases used in buffer solutions?

Buffer solutions play a crucial role in maintaining a stable pH when strong acids or bases are introduced. Weak acids and bases are particularly effective in this regard because they partially dissociate in solution. This means there is an equilibrium between the weak acid and its conjugate base (or the weak base and its conjugate acid).

When a strong acid is added to the buffer solution, the weak base present can react with the added protons, minimizing the increase in hydrogen ion concentration. Conversely, if a strong base is added, the weak acid present can donate protons to counteract the increase in hydroxide ions. This ability to provide or absorb protons makes buffers effective at resisting significant changes in pH.

Therefore, the correct answer highlights that the use of weak acids and bases in buffers is specifically due to their capacity to resist changes in pH when external strong acids or bases are introduced into the system. This property is essential in many biological and chemical systems where maintaining a relatively constant pH is critical for proper function and stability.