# What is a diprotic acid?

${\text{H"_2"Y"(aq) +"2H"_2"O"(l) rightleftharpoons2"H"_3"O"^+ + "Y}}^{2 -}$
And some examples of diprotic acid, (i) $\text{sulfuric acid}$, ${\text{H"_2"SO}}_{4}$; (ii) $\text{oxalic acid}$, $\text{HO(O=)CC(=O)OH}$; (iii) $\text{sulfurous acid}$, ${\text{H"_2"SO}}_{3}$; (iv) $\text{phosphoric acid}$, ${\text{H"_3"PO}}_{4}$, which acts as a diacid in water.