General Free Energy Changes de Donders Affinity

3 GENERAL FREE ENERGY CHANGES DE DONDER S AFFINITY 

A more general picture of the free energy driving forces accompanying chemical reaction can be given in terms of de Donder s affinity 4, defined as 

Although not a literal force in the mechanical sense (cf. Sidebar 2.8), affinity plays an analogous role in driving the reaction toward equilibrium, where 4 = 0 [cf. (8.11)]. For general nonequilibrium A eq, we can recognize that 

The approach to equilibrium is therefore characterized by the following (equivalent) conditions  

The expression for Keq in (8.27d) shows that if AG° 0 ( exoergic ), then Keq 1, and the reaction lies toward the product side at equilibrium. Conversely, if AG° 0 ( endoergic ), then Koq 1, and equilibrium lies toward the reactant side. 

---