Chemistry 12 · Chemistry · Lesson 5.2
The chemistry of buffers
- Level
- Grade 12
- Reading time
- 11 min reading
- Review
- Last reviewed 2026-09-03
- Standard
- Accuracy standard
- Errata
Abstract
Solutions that resist changes in pH.
What is a buffer solution?
Short answer
A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It contains a weak acid and its conjugate base (or a weak base and its conjugate acid) in comparable amounts; one component neutralizes added base and the other neutralizes added acid. Buffers keep systems like blood at a nearly constant pH.
Concept preview
What you will be able to do
- 01Explain how a buffer resists a change in pH
- 02Use the Henderson-Hasselbalch equation to find or design a buffer pH
- 03Explain buffer capacity
Some solutions hold their pH almost constant even when acid or base is added; these are buffers. A buffer is a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid), present together in comparable amounts. The essential requirement is that both members of a conjugate pair be present in significant quantities — one to neutralise added base, and the other to neutralise added acid.
School Plan
The chemistry of buffers
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Related topics
Frequently asked questions
- How does a buffer resist pH change?
- Its weak-acid component neutralizes added base and its conjugate-base component neutralizes added acid, keeping [H⁺] nearly constant.
- Why is blood a buffered solution?
- The carbonic acid–bicarbonate buffer keeps blood pH near 7.4, which is essential for enzyme and cell function.