Buffer chemistry rests on Le Chatelier's Principle: a solution containing a weak acid (HA) in equilibrium with its conjugate base (A⁻) resists large pH shifts because the equilibrium shifts to replenish whichever species (H⁺ or OH⁻) is consumed when a strong acid or base is added, unlike pure water where the same addition produces a dramatic pH change. This buffering behavior is quantified by the Henderson-Hasselbalch equation, pH = pKa + log([A⁻]/[HA]), derived directly from the acid dissociation equilibrium constant expression (Ka = [H⁺][A⁻]/[HA]) by solving for [H⁺] and taking the negative log of both sides. This belongs to acid-base equilibrium chemistry, relating solution pH to the equilibrium constant (Ka/pKa) and the ratio of conjugate acid-base concentrations.
Buffer chemistry rests on Le Chatelier's Principle: a solution containing a weak acid (HA) in equilibrium with its conjugate base (A⁻) resists large pH shifts because the equilibrium shifts to replen…