The Effect of AH, AS, and T on Spontaneity

Case 1 AH Negative, AS Positive If a reaction is exothermic (AH 0), and if the change in entropy for the reaction is positive (AS 0), then the change in free energy is negative at all temperatures and the reaction is spontaneous at all temperatures. 

M FIGURE 17.7 Gibbs Free Energy Gibbs free energy is also called chemical potential becanse it determines the direction of spontaneons change for chemical systems. 

Recall from Chapter 6 that AH° represents the standard enthalpy change. The definition of the standard state was first given in Section 6.9 and is summarized in Section 17.6. 

As an example, consider the formation of ozone from oxygen  

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