What Is a Buffer? How Solutions Resist pH Change
Add one drop of strong acid to a glass of pure water and the pH crashes from 7 to about 3. Add the same drop to your bloodstream and nothing happens — your pH shifts by maybe a hundredth of a unit. The difference is a buffer, and without it you would not survive lunch. The short answer: a buffer is a solution that resists changes in pH when small amounts of acid or base are added. It works because it contains a weak acid and its conjugate base side by side, one ready to mop up added OH⁻ and the other ready to mop up added H⁺. What a buffer actually is A buffer needs two components present in comparable amounts: a weak acid (call it HA), and its conjugate base (A⁻) — the same species minus its proton. The classic laboratory buffer is acetic acid (CH₃COOH) with sodium acetate (CH₃COONa) . The acetic acid supplies HA; the sodium acetate dissolves to supply A⁻. The pair works because a weak acid sits in equilibrium rather than committing one way: CH₃COOH ⇌ H⁺ + CH₃COO⁻ Having...