6.2. Equilibrium - II (icon Equilibrium) — Chemistry STD 11 Science — Question

According to the theory:

Acids are proton $\left( H ^{+}\right)$donors.

Bases are proton $\left( H ^{+}\right)$acceptors.

Hence, in order to get the conjugate base of a species, we should consider that substance as an acid and vice versa.

For example,

$H _2 SO _4 \rightarrow HSO _4^{-}+ H ^{+}$

Therefore, conjugate base of $H _2 SO _4$ is $HSO _4^{-}$.

Using this logic, for the given example:

$H _2 PO _4^{-} \rightarrow HPO _4^{-2}+ H ^{+}$

Hence, conjugate base of $H _2 PO _4^{-}$is $HPO _4^{-2}$.