Why do buffers resist pH change?

1 Answer
May 28, 2016

Answer:

Because they introduce a means for the solvent to sop up excess #H_3O^+# and #HO^-#, and resist gross change in #pH#.

Explanation:

This equation is well-known:

#pH=pK_a+log_10{[[A^-]]/[[HA]}}#

Thus given quantities of acid and conjugate base, added #H_3O^+# or #HO^-# reacts with the base or the acid, and #pH# change is moderated by the #log_10# term.

When a weak acid is titrated by a strong base, or a strong acid by a weak base, a buffer is formed initially, and this region of the graph of #pH# versus volume of titrant is known as the buffer region.

Biological systems are extensively buffered, to reduce gross changes in #pH#.

For a fuller treatment, see this old answer.