THE FREE ENERGY-EMF RELATION

The change in free energy (AG) is the maximum amoimt of enei that is available to do useful work. In an electrochemical cell, this free energy is equal to electrical work which is equal to the product of the number electrons, the Faraday constant, and the electrochemical cell s emf. 

In this equation, n is the number of equivalents of electrons transferred in the reaction, F is the Faraday constant (96,500 coulombs), and (cell s emf). From 

Calculate the standard free energy change at 25°C for the redox reaction in Example 12-1. (Faraday constant = 96,500 coulombs) 

From the previous example, we know that the emf of this reaction is 1.10 V. The formula for AG in terms of the potential difference is  

the number of electrons transferred is 2. This number is obtained by examining the balanced equation and evaluating the change in oxidation numbers. For example, copper ions with +2 oxidation state changed to copper (solid) with an oxidation state of 0. In other words, each half-reaction involves two electrons. 

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