During the step-wise titration of the polyprotic acid with aqueous , distinct buffer regions are est — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

$H_3PO_4$ neutralizes in three separate stages corresponding to its three ionizable protons. In the first stage, the buffer pair is $H_3PO_4 / H_2PO_4^-$. In the second stage, the pair is $H_2PO_4^- / HPO_4^{2-}$. In the third stage, it is $HPO_4^{2-} / PO_4^{3-}$. Option D is physically incorrect as the species differ by two protons and do not form a simple conjugate buffer pair.