# How can you tell conjugate acid and base pairs apart?

By adding or subtracting ${H}^{+}$.........
By adding or subtracting ${H}^{+}$ and conserving mass and charge. The conjugate base of any acid, $H A$, is ${A}^{-}$, and the conjugate acid of any base $H A$ is ${H}_{2} {A}^{+}$. In both these instances MASS and CHARGE have been conserved.
It is trivial to determine the conjugate base of $H X$, i.e. it is the original acid LESS a proton, i.e. ${X}^{-}$. And the conjugate acid of $H X$ is ${H}_{2} {X}^{+}$. For both examples we started with a definite substance, here $H X$, to which we added or subtracted ${H}^{+}$.
Can you tell me the conjugate acid and conjugate base of sulfuric acid, ${H}_{2} S {O}_{4}$?