Suppose that you are in an engineering competition in which commercial power sources are prohibited. You might decide to use a Daniell cell to power a model electric car. You will need to know the potential of the cell corresponding to the concentrations of reagents you intend to use. The potential difference generated by the Daniell cell in which solutions of 1.00 mol · L^–1 zinc and 0.01 mol · L^–1 copper ions are used is +1.04 V. What is the reaction Gibbs free energy for this cell under these conditions?

ANTICIPATE Because the cell generates a positive electric potential, the reaction is spontaneous under the conditions of the experiment, so you should expect to find that the Gibbs free energy of reaction is negative.

PLAN Use Eq. 1a to determine the reaction Gibbs free energy for reaction A from the cell potential. Identify the value of n from the balanced equation (reaction A). In more complicated cases, you might need to refer to the two matched half-reactions.

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AG - nFEcell (la)