Buffers

BUFFERS

Figure 57.

Buffers are weak mixtures of weak acids and its conjugate base or a mixture of a weak base and its conjugate acid. These are helpful in biological systems because they resist changes in pH when small amounts of strong acids or bases are added. Acetic acid and sodium acetate together are a buffer solution that will resist wide pH shifts. Ammonia and ammonium chloride also represent a buffer system.

Buffers are buffers because they contain weak acids or bases and their salts. They can “soak up” or combine with hydroxide ions or hydronium (H3O+) ions to keep the pH roughly the same within certain limits. In biological systems, there is a phosphate buffer system, protein buffer systems, and the carbonic acid system—each of which keeps the pH steady in biological systems. It doesn’t matter whether OH- is added or hydronium ion is added, there will be the prevention of a pH change.

Buffer solutions are not unlimited in their capacity to maintain a constant and steady pH. If there is an acetic acid/acetate buffer system and a lot of base is added, the buffering capacity will be exhausted, eve if not all of the buffer is exhausted. As the buffering action is depleted, the buffering action will not be as effective. The more buffering acids/bases and salts that are added to the system, the better the buffering capacity will be.