## Chemistry 12th Edition

Bronsted acids: $H_3PO_4$ and $H_3O^+$ Bronsted base: $PO_4^{3-}$ Both: $H_2PO_4^-$ and $HPO_4^{2-}$
Phosporic acid ($H_3PO_4$) is a polyprotic acid, its first reaction is: (I) $H_3PO_4(aq) + H_2O(l) H_2PO_4^-(aq) + H_3O^+(aq)$ But, $H_2PO_4^-$ is also an acid: (II) $H_2PO_4^-(aq) + H_2O(l) HPO_4^{2-}(aq) + H_3O^+(aq)$ And $HPO_4^{2-}$ too: (III) $HPO_4^{2-}(aq) + H_2O(l) PO_4^{3-}(aq) + H_3O^+(aq)$ Now, as we can analyze these are all the species present in the solution: Bronsted acids: $H_3PO_4$ and $H_3O^+$ (Donate a proton) Bronsted base: $PO_4^{3-}$ (Receives a proton) Both: $H_2PO_4^-$ and $HPO_4^{2-}$ (Donate and receive a proton)