What is the Henderson-Hasselbalch equation?

The Henderson-Hasselbalch equation is a mathematical expression that relates the pH of a solution to the pKa (acid dissociation constant) and the ratio of the concentrations of the conjugate base and the weak acid. It is derived from the acid dissociation equilibrium and is given by: pH = pKa + log10([A⁻]/[HA]), where [A⁻] is the concentration of the conjugate base and [HA] is the concentration of the weak acid. This equation is fundamental in understanding buffer solutions and acid-base equilibria.