Ferric ion is not very soluble at neutral \(\mathrm{pH}\). (The \(\mathrm{K}_{\mathrm{sp}}\) for \(\mathrm{Fe}(\mathrm{OH})_{3}\) is \(\sim 3 \times 10^{-38}\).) Yet evidence of iron is often observed in water pumped directly from simple, hand-operated pumps in rural locations. (It is noticeable in the taste of the water and in the dark reddish-orange stain on the concrete support where water from the pump splashes.) Use the concept of \(E_{\mathrm{H}}\) to describe the mechanism that solubilizes iron in the water deep in the ground water and leads to the rust color on the concrete base at the surface.