Answer is: H₃PO₄.
A phosphoric acid is three protic acid, which means that in water release tree protons. Phosphoric acid ionizes in three steps in water.
First step: H₃PO₄(aq) ⇄ H₂PO₄⁻(aq) + H⁺(aq).
Second step: H₂PO₄⁻(aq)⇄ HPO₄²⁻(aq) + H⁺(aq).
Third step: HPO₄²⁻(aq) ⇄ PO₄³⁻(aq) + H⁺(aq).
Species that are present: H₃PO₄,
H₂PO₄⁻, HPO₄²⁻, PO₄³⁻ and H⁺, but because the acid dissociation constants are low, very low percentage of acid dissociates.
