# How would you identify the conjugate acid-base pairs in the equilibrium equation: HC2H3O2 + H2O --> H3O^+ + C2H3O2^-?

${H}_{3} C - C \left(= O\right) O H \left(a q\right) + {H}_{2} O r i g h t \le f t h a r p \infty n s {H}_{3} C - C \left(= O\right) {O}^{-} \left(a q\right) + {H}_{3} {O}^{+}$
The conjugate base of acetic acid is the acetate anion (the parent acid less a proton, ${H}^{+}$), hence ${H}_{3} C - C \left(= O\right) {O}^{-}$. The conjugate acid of $O {H}_{2}$ is water plus a proton, i.e. an hydronium ion, ${H}_{3} {O}^{+}$. This is a representation, and as far as anyone knows the hydronium ion is a cluster of 3-4 water molecules (say ${O}_{3} {H}_{6}$) plus a proton to give ${H}_{7} {O}_{3}^{+}$. To represent the reactivity of this species in aqueous solution, ${H}^{+}$ or ${H}_{3} {O}^{+}$, are entirely appropriate shorthands.