Effect of Gas Concentration—The Nernst Equation

In this section, we will consider the effect of species concentration in reactant and product gas mixtures on the change of Gibbs function reaction and 

All terms representing the standard Gibbs function terms can be grouped as a change of standard Gibbs function term as 

representing the change of Gibbs function in terms of cell voltage given by Equations 4.16 and 4.21, we get 

This equation can also be generalized for a reaction with arbitrary number of reactants and products as 

Since partial pressure of the gas species in reactant and product gas mixtures are represented by the gas concentration or mole fraction through the 

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