The conjugate base of $\mathrm{H}_2 \mathrm{PO}_4^{-}$is :

Question

Professor PC Thomas Classes · Answer

(c) $\mathrm{HX} \rightleftharpoons \mathrm{H}^{+}+X^{-}$ 
If, $\mathrm{HX} \rightarrow$ acid 
then, $X^{-} \rightarrow$ conjugate base