Electromotive Force of Fuel Cell

Gibbs energy is basically free energy available for conversion into usable work. The change in Gibbs free energy is given by 

The Gibbs free energy of formation Gf can also be expressed in terms of products and reactants as follows  

We can demonstrate the Gibbs energy of formation with the help of the following reaction  

The total electric work done in moving -2F charge around the ceU-circuit, for E voltage (ideal potential) of fuel cell is given by 

This work released Gibbs free energy (provided the system is reversible and has no losses). 

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