Chemistry
Chemistry
Problem
Why must buffer solutions be composed of weak acid or base conjugate systems, not of strong acids or bases?Intuitive explanation
A buffer resists pH change by having two forms of the same species that can neutralize added acid or base. Strong acids and bases completely dissociate, leaving no reservoir of the opposite form to absorb disturbances—a strong acid has no conjugate base present to neutralize added base, and vice versa. Weak acid–conjugate base pairs, however, maintain both forms in equilibrium, so each can respond when the pH is pushed in either direction.
Intuitive explanation
A buffer resists pH change by having two forms of the same species that can neutralize added acid or base. Strong acids and bases completely dissociate, leaving no reservoir of the opposite form to absorb disturbances—a strong acid has no conjugate base present to neutralize added base, and vice versa. Weak acid–conjugate base pairs, however, maintain both forms in equilibrium, so each can respond when the pH is pushed in either direction.