What is the pH of a 1.0 M H2SO3 solution?
(K1 = 1.2 x 10-2, and K2 = 6.6 x 10-8
....................H2SO3 ==> H^+ + HSO3^-
I....................1 ..................0..........0
C...................-x..................x..........x
E.....................1-x...............x..........x
k1 = 0.012 = (H^+)(HSO3^-)/(H2SO4)
0.012 = (x)(x)/(1-x)
Solve for x = (H^+) and convert to pH. I have ignored any contribution by k2 since it is so much weaker than k1. For every 5,500000 H^+ from k1 you get 1 H^+ from k2 so the k2 contribution is negligible.