Diprotic acid
A diprotic acid is an acid such as H2SO4 (sulfuric acid) that happens to contain within its molecular structure two hydrogen atoms capable of dissociation (i.e. ionizable) in water. The complete dissociation of diprotic acids is of the same form as sulfuric acid:
H2SO4 → H+(aq) + HSO4−(aq) Ka = 1 × 103
HSO4− → H+(aq) + [...]