This problem is driving me nuts. :tongue2: The polyprotic acid, H2SO4 has a complete disassociation at the first step and its pKa for the second step is 1.9. When CaSO4 dissolves ina strong acidic solution of HCl, the final concentration of Ca2+ is 0.03 M and [SO42-] is 0.008 M. What is the pH of the solution? Okay, so I did the equilibrium for the first reaction. Doesn't tell me much except that I see it produces hydronium and sulfate at the end of the second step... H2SO4 + H2O -> H3O+ (aq) + HSO4- (aq) then HSO4- (aq) + H2O (l) -> H3O+ (aq) + SO42- (aq) ...the second reaction seems to produce sulfate as well, but I can't quite figure out how to tie them together, mostly because I can't figure out how the second equilibrium reaction works. Working from CaSO4 + H2O -> Ca2+ + SO42- This seems too simple... do I need to add HCl and H2O on the left? If so then I get a chloride ion on the right that I don't have a concentration for, ditto for the hydronium... of course, since I'm just adding stuff to both sides, it doesn't matter, does it. Still, it seems like I'm missing something I'd need to find Kb. Anyway, I'm presuming that if I could figure out this second reaction I could work out Kb and thus pKb, then pOH, pH, success. Although that leaves out the given pH... ugh. Stuck.