At what point will a buffer solution cease to moderate changes in pH?

Question

Quizplus · Accepted Answer

A buffer solution works by having a weak acid and its conjugate base (or a weak base and its conjugate acid) present in solution. When an acid or base is added, the buffer system can neutralize it through the acid-base reaction. However, once all of the buffering components have been neutralized, the buffer solution ceases to moderate changes in pH and becomes ineffective. Choice A is incorrect because the equilibrium constant of water is not directly related to buffer capacity. Choice B is incorrect because equal concentrations of weak acid and weak base will still maintain buffering capacity as long as some of each component remains unreacted. Choice D is incorrect because a buffer solution can continue to moderate changes in pH even if not all of the acid or base has been added.

At What Point Will a Buffer Solution Cease to Moderate