Henderson–Hasselbalch equation

In chemistry and biochemistry, the pH of weakly acidic chemical solutions can be estimated using the Henderson-Hasselbalch Equation: pH = p K a + log 10 ⁡ ( [ Base ] [ Acid ] ) {\displaystyle {\ce {pH}}={\ce {p}}K_{{\ce {a}}}+\log _{10}\left({\frac {[{\ce {Base}}]}{[{\ce {Acid}}]}}\right)} The equation relates the pH of the weak acid to the numerical value of the acid dissociation constant, Ka, of the acid, and the ratio of the concentrations of the acid and its conjugate base. Acid-base Equilibrium Reaction H A ( a c i d ) ⇋ A − ( b a s e ) + H + {\displaystyle \mathrm {{\underset {(acid)}{HA}}\leftrightharpoons {\underset {(base)}{A^{-}}}+H^{+}} } The Henderson-Hasselbalch equation is often used for estimating the pH of buffer solutions by approximating the actual concentration ratio as the ratio of the analytical concentrations of the acid and of a salt, MA. It is also useful for determining the volumes of the reagents needed before preparing buffer solutions, which prevents unnecessary waste of chemical reagents that may need to be further neutralized by even more reagents before they are safe to expose.

Source: Wikipedia — Henderson–Hasselbalch equation (CC BY-SA 4.0)