[Erica]

Ok, here is the problem:

Given the following half-rxns:
(1) M(s) + 6 H2O(l) ---> M(OH2)63+(aq) + 3 e- E° = 0.058 V;

(2) M(OH2)62+(aq) ---> M(OH2)63+(aq) + 1 e- E° = -0.448 V; and

(3) M(s) + CO32-(aq) ---> MCO3(s) + 2 e- E° = 1.069 V;

calculate the solubility product of MCO3(s) and specify it to 3 significant digits in mathematical notation. Assume all processes to take place at 298.2 K and use appropriate constants F and R to at least 4 significant digits.

My work:
I attempted to add the first two half reactions together and then try and add the third, but if you find the Eo of the first two reactions, the e's dissappear...so what am I supposed to do? I guess I'm pretty much stuck, I feel like its a simple problem, but I'm definately missing something. I'm not even really sure which equation to use, or how to set it up.
I've tried looking at examples in the book, but they only show what to do with two half cell reactions, not three.
Thanks in advance to any help, I'd really appreciate it.