# How does pKa change with pH?

pH = pK_a + log (A^-/HA)
pH = pK_a + log (A^-/HA)
pKa is an equilibrium constant. pH is an indication of hydrogen ion content in a solution. Any changes to pH will therefore affect one of the factors in the pKa equation. The amount and direction of change in the pKa value will depend on whether the ${H}^{+}$ ions are part of the reactant or product side of the equation.