Question

Using chemical equations, show how the triprotic acid H3PO4 ionizes in water. Phases are optional.

Answer 1

$H_3PO_4 ==> H^+ + H_2PO_4^- \ \ ... Ka_1\\ H_2PO_4^- ==> H^+ + HPO_4^{2-}\ \ ... Ka_2\\ HPO_4^{2-} ==> H^+ + PO_4^{3-} \ \ \ \ \ ... Ka3 \\ \\ \\Ka_1 = [H^+][H_2PO_4^-]/[H_3PO_4] \\ Ka_2 = [H^+][HPO_4^{2-}][H_2PO_4-]\\ Ka_3 = [H^+][PO_4^{3-}]/[HPO_4^{2-}]$