For sulfurous acid (h2so3, a diprotic acid) write the equilibrium dissociation reactions and the corresponding expressions for the equilibrium constants

Since the acid is diprotic, there are two equilibrium dissociation reactions for it. Consequently, there will also be two expression for equilibrium constants, Ka₁ and Ka₂.

First reaction:
H₂SO₃ ⇄ 2H⁺ + HSO₃²⁻          >     Ka₁ = [H⁺][HSO₃²⁻]/[H₂SO₃]

Second reaction:
HSO₃²⁻ ⇆ H⁺ + SO₃²⁻             >     Ka₂ = [H⁺][SO₃²⁻]/[HSO₃²⁻]