pH = pKa + log Examining this version of the Henderson-Hasselbalch equation reveals some
additional properties of buffers.
If you’re given the number of moles of HA and A− in the test question,
don’t waste time converting to molarity just to plug into the Henderson-
Hasselbalch equation; just use moles.
- If the number of moles of HA and A− are equal, then the Henderson-
Hasselbalch equation can be simplified to pH = pKa (or pOH = pKb). - The pH of a buffer solution doesn’t change with changing volume, since
volume does not appear in the equation. Therefore, diluting or
concentrating (through evaporation or osmosis) a buffer will not change its
pH.
The third point is arguably the most important chemical property of a buffer, so
memorize it.
Diluting or concentrating a buffered solution does not change its pH.