Buffers

Science

Definition

A buffer is a solution that resists changes in pH when small amounts of acid or base are added. Buffers consist of a weak acid and its conjugate base (or a weak base and its conjugate acid) that work together to neutralize added H⁺ or OH⁻ ions.

Examples

  • Blood is buffered at pH 7.35–7.45 primarily by the carbonic acid–bicarbonate system (H₂CO₃/HCO₃⁻)
  • A mixture of acetic acid and sodium acetate creates a buffer around pH 4.75
  • Buffer solutions are essential in biology labs to maintain stable pH conditions for enzyme experiments
Key Fact

Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA]); buffers work best when pH ≈ pKa ± 1.

Related Terms

Ph scale Acid-base theory Strong vs weak acids Ph calculations

Study This Concept

Practice buffers with free review games in these units:

AP Chemistry Unit 8: Acids and Bases