The Gibbs Free Energy of a Chemical Reaction System As a Function of the Extent of Reaction and the Prediction of Spontaneity

Students often have a very simplistic idea of the relationship between the value of ∆G° for a reaction and the reaction's spontaneity: if ∆G° is negative, the reaction is spontaneous; if it is positive, the reaction is not spontaneous and in fact is anti spontaneous, going spontaneously in the reverse direction. This exercise is designed to help students develop a more nuanced understanding of the relationship between ∆G°rxn and spontaneity through the creation of a graph of G for a reaction mixture vs. the extent of reaction, ζ, and an exploration of how the shape of that graph is affected by the value of ∆G° rxn .