1. The problem statement, all variables and given/known data Calculate the pH of rainwater in equilibrium with SO2 in a polluted air mass for which the sulfur dioxide concentration is 1ppm. SO2(g) +H2O(g) = H2SO3(aq) Kh=1M/atm H2SO3 = HSO3- + H+ Ka=1.7x10-2M 2. Relevant equations 3. The attempt at a solution I'm pretty lost for this one. I converted SO2 1 ppm to 1E-6 atm. Set up EQ expression but have two unknowns. 1 M/atm = (1E-6 atm)[H2O] / [H2SO3] I don't know where to go from here. Even if I figure can calculate H2SO3 I'll still have two unknowns in second reaction. I don't think water can be 1 M as it is not a liquid. Please can someone give me a suggestion where to start.