[Big-Daddy]

A lot of theory I have seen on redox reactions focuses on measuring equilibrium constants for these reactions using electrode potentials etc. But now I am trying to find out how to calculate equilibrium concentrations in redox systems, given all equilibrium constants, and don't know how to do it.

Say e.g. I drop iron in water. The equilibria are Fe³⁺ + e^-  Fe²⁺, Fe²⁺ + 2e^-  Fe, H2O  H⁺ + OH^-, O₂ (g) + 4H⁺ + 4e^-  H₂O, 2H⁺ + 2e^-  H₂ (g).

I can see no way to write the equilibrium system of equations this time. Even if we are given K values for all equilibria above. Yet I find this is a central question in order to understand redox equilibrium.