Buffer: definition in chemistry
Buffer: A solution that resists changes in pH when small amounts of acid or base are added. It usually contains a weak acid and its conjugate base, or a weak base and its conjugate acid.
In a buffer made of acetic acid and acetate ions, added base is neutralized by the acetic acid and added acid is taken up by the acetate ions, so the pH barely moves. A buffer works best near the pH where its acid and base forms are present in equal amounts, and it stops working once one form is used up. Buffers keep the pH of blood, cells and many industrial and laboratory processes within narrow limits.
Examples
- Blood — carbonic acid and hydrogen carbonate keep pH near 7.4
- Acetic acid and sodium acetate — a buffer near pH 4.8
- Ammonia and ammonium chloride — a buffer near pH 9.3
- Standard buffer solutions used to calibrate pH meters