Equilibrium – NEET UG ChemistryPractice Questions & PYQs

The dissociation behavior of a polyprotic acid is governed by the energy required to remove each successive proton from the molecular structure. In the first step, the proton is released from a neutral molecule:
$\mathrm{H}_2\mathrm{A} \rightleftharpoons \mathrm{H}\mathrm{A}^- + \mathrm{H}^+$
However, the second dissociation step involves separating a positively charged proton from a negatively charged anion, which is significantly more difficult due to the electrostatic attraction between the species:
$\mathrm{H}\mathrm{A}^- \rightleftharpoons \mathrm{A}^{2-} + \mathrm{H}^+$
Because this Coulombic barrier makes it harder to lose the second proton than the first, the dissociation constants must satisfy the relationship $K_{a_1} > K_{a_2}$.