Reaction spontaneity and the direction of thermodynamic change

We start by introducing the concept of entropy S to explain why some reactions occur spontaneously, without needing additional energy, yet others do not. The sign of A 5 for a thermodynamic universe must be positive for spontaneity. We explore the temperature dependence of A5. 

In the following sections, we introduce the concept of a thermodynamic universe (i.e. a system plus its surroundings). For a reaction to occur spontaneously in a system, we require the change in Gibbs function G to be negative. We then explore the thermodynamic behaviour of G as a function of pressure, temperature and reaction composition. 

Finally, we investigate the relationship between AG and the respective equilibrium constant K, and outline the temperature interdependence of AG and K. 

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