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⁺.
