Consider the cell potentials E∘Mg2+|Mg = −2.37V and E∘Fe2+|Fe = −0.04V . The best reducing agent among the above would be:

To determine the best reducing agent among the given options, we need to compare their cell potentials. The cell potential is a measure of the tendency of a species to be reduced.

The cell potential for the reduction of Mg2+ to Mg is -2.37V, while the cell potential for the reduction of Fe2+ to Fe is -0.04V.

The more negative the cell potential, the stronger the reducing agent. Therefore, the species with the more negative cell potential is the better reducing agent.

In this case, Mg2+ has a more negative cell potential (-2.37V) compared to Fe2+ (-0.04V). Therefore, Mg2+ is the better reducing agent among the given options.