Statement 1 : Acids that have more than one proton that can be donated to base are called polyprotic acids.

Statement 2 : For all diprotic acids, the equilibrium constant $K_{a_2},$ for the second stage of ionisation is smaller than the equilibrium constant, $K_{a_1},$ for the first stage of ionisation.

A polyprotic acid is a compound which may lose more than 1 proton.  The constant for dissociation of the first proton may be denoted as ${\mathrm{K}}_{{\mathrm{a}}_1}$ and the constants for dissociation of successive protons as ${\mathrm{K}}_{{\mathrm{a}}_2}$, etc. Phosphoric acid, H₃PO₄, is an example of a polyprotic acid as it can lose three protons.

In polyprotic acids, ${\mathrm{K}}_{{\mathrm{a}}_1}>{\mathrm{K}}_{{\mathrm{a}}_2}>{\mathrm{K}}_{{\mathrm{a}}_3}>...$