Reaction quotient its

The reaction quotient, Q, was introduced in Section 17-4. It involves a ratio of concentrations or pressures of products to those of reactants, each raised to the power indicated by the coefficient in the balanced equation. The Q expression that is used in the Nernst equation is the thermodynamic reaction quotient it can include both concentrations and pressures. Substituting these values into the Nernst equation at 25°C gives... 

Here Q is the thermod3mamic form of the reaction quotient. It has the same general appearance as the thermod3mamic equilibrium constant K, but the concentrations and partial pressures are those for a mixture at some instant, perhaps at the beginning of a reaction. You obtain AG from AG° by adding KTln Q, where In Q is the natural logarithm of Q = 2.303 log 0. 

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