# Is sulfuric acid a diprotic acid?

Apr 19, 2017

$\text{Sulfuric acid}$ is a diprotic reagent.......

#### Explanation:

The conjugate base of sulfuric acid is bisulfate ion, $H S {O}_{4}^{-}$, which itself is a strongish Bronsted acid:

${H}_{2} S {O}_{4} \left(l\right) + {H}_{2} O \left(l\right) \rightarrow H S {O}_{4}^{-} + {H}_{3} {O}^{+}$

And $H S {O}_{4}^{-} + {H}_{2} O \left(l\right) \rightarrow {H}_{3} {O}^{+} + S {O}_{4}^{2 -}$

Overall,

${H}_{2} S {O}_{4} \left(a q\right) + 2 {H}_{2} O \rightarrow 2 {H}_{3} {O}^{+} + S {O}_{4}^{2 -}$

You will have to look up the ${K}_{a}$ for $H S {O}_{4}^{-}$, but we generally assume that sulfuric acid is diprotic in aqueous solution.