Provide the Equation That Relates the Equilibrium Constant, K_eq, to the Acid

Short Answer

Provide the equation that relates the equilibrium constant, K_eq, to the acid dissociation constant, K_a, for the following equilibrium. $\mathrm{HA}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{A}^{-}+\mathrm{H}_{3} \mathrm{O}^{+}$