Chapter 18, Problem 18.151CP

At one time on Earth, iron was present mostly as iron(ll). Later, once plants had produced a significant quantity of oxygen in the atmosphere, the iron became oxidized to iron(lll). Show that ${\text{Fe}}^{2+}\left(aq\right)$can be spontaneously oxidized to ${\text{Fe}}^{3+}\left(aq\right)$by ${\text{O}}_2\left(g\right)$at 25 °C assuming the following reasonable environmental conditions: $\begin{array}{l}\left[{\text{Fe}}^{2+}\right]=\left[{\text{Fe}}^{3+}\right]=1\times {10}^{-7}\text{M;}\text{pH}=7.0;P{o}_2=160\text{mm}\text{Hg}\\ \end{array}$.