Final answer:
If the pH of a solution is too high, an acid can be added to lower it. A buffer, which consists of a weak acid or base and its salt, is used to resist drastic pH changes when acids or bases are added. The ability of a buffer to maintain pH stability is quantified by its buffer capacity.
Step-by-step explanation:
If the pH of a solution is too high, an acid can be added as a buffer to lower pH. Buffers are solutions that consist of a weak acid or base and its corresponding salt, which work together to resist changes in pH. When an acid is added to a buffer, it reacts with the base component of the buffer, thereby reducing the potential increase in hydrogen ion concentration and preventing a large change in pH. This action is akin to how a sponge absorbs water, with the buffer absorbing excess hydrogen or hydroxide ions. The buffer capacity is the measure of how much acid or base the buffer can neutralize before there is a significant change in the pH of the solution.
Buffers are particularly important in biological and chemical systems where maintaining a stable pH is crucial. For instance, human blood contains a buffer system that helps maintain its pH within a very narrow range. Without this mechanism, any small addition of acid or base could drastically change the pH, leading to harmful effects on cellular processes.