According to Bronsted-Lowry theory of acids and bases, an acid is proton donor and a base is proton acceptor. When an acid loses the proton, it forms the conjugate base of the acid. Similarly when a base accepts a proton, it forms the conjugate acid if that base. A conjugate acid base pair differs by a single proton.
Given the weak acid [tex]CH_{3}COOH[/tex]. It can lose a proton to form the conjugate base.
[tex]CH_{3}COOH(aq)-->CH_{3}COO^{-}(aq)+H^{+}(aq)[/tex]
Therefore, the conjugate base of [tex]CH_{3}COOH[/tex]is [tex]CH_{3}COO^{-}[/tex].
