# What is the conjugate for benzoic acid, (HC7H5O2)?

The conjugate base of benzoic acid, ${C}_{6} {H}_{5} C \left(= O\right) O H$, is benzoate, ${C}_{6} {H}_{5} C \left(= O\right) - {O}^{-}$.
The conjugate base of any any acid is simply the parent acid, $H A$, less a proton, ${H}^{+}$. Mass and charge are conserved. On the other hand, the conjugate acid of any base, ${A}^{-}$, is simply $H A$, that is the parent base plus a proton, ${H}^{+}$.
Given this treatment, what is the conjugate base of hydroxide anion, $H {O}^{-}$?