Suppose that you work for a company that designs the drive mechanisms for large ships.

The materials in this mechanism will obviously come into contact with environments that enhance corrosion. To estimate the difficulties that corrosion might cause, you decide to build a model electrochemical cell using electrolyte concentrations that might be present in your system when it is in service. Assume that you have a cell that has an iron(II) concentration of 0.015 M and an H⁺ concentration of 1.0 × 10^–3 M.

The cell temperature is 38°C, and the pressure of hydrogen gas is maintained at 0.04 atm. What would the cell potential be under these conditions?

Strategy 

This problem defines nonstandard conditions that must be addressed using the Nernst equation. Virtually anytime you are given concentrations of electrolytes present in a cell (other than 1 M), you will need this equation. This problem also presents the challenge of identifying the reactions involved. Iron will be the anode, but we will need to scan the table of standard reduction potentials to identify a possible cathode reaction. The most likely suspect is the reduction of H⁺ to H₂. Once we know both half-reactions, we can calculate the standard cell potential and fill in the appropriate values in the Nernst equation.