Calculate the concentrations of all species in a 1.22 M Na2SO3 (sodium sulfite) solution. The ionization constants for sulfurous acid are Ka1 = 1.4× 10–2 M and Ka2 = 6.3× 10–8 M.

Answer 1

.........SO3^2- + H2O --> HSO3^- + OH^-
I........1.22..............0........0
C.........-x...............x........x
E.......1.22-x.............x........x

Kb1 for SO3^2- = (Kw/Ka2 for H2SO3) = (x)(x)/(1.22-x)
Solve for x = OH^- . That gives you SO3^2-, HSO3^- and OH^-.

.........HSO3^- + H2O ==> H2SO3 + OH^-
I.......above..............0.......
C.........-x...............x.......x
E.......above-x............x.......x

Kb2 for HSO3^- = (Kw/Ka1 for H2SO3) = (H2SO3)(OH^-)/(HSO3^-) = k2
Since the (OH^-) = (HSO3^-), then H2SO3 = k2.