The Gibbs Free Energy of a Chemical Reaction System As a Function of the Extent of Reaction and the Prediction of Spontaneity
Arthur Ferguson
Department of Chemistry, Worcester State College, Worcester, MA 01602-2597
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Abstract
Students often have a very simplistic idea of the relationship between the value of ΔGº for a reaction and the reaction's spontaneity: if ΔGº 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 ΔrxnGº and spontaneity through the creation of a graph of G for a reaction mixture vs. the extent of reaction, ξ, and an exploration of how the shape of that graph is affected by the value of ΔrxnGº (Figure 1).
Figure 1. The free energy, G kJ/mole, of a reaction as a function of the extent of that reaction ξ.
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KeywordsComputer-Based Instruction; Equilibrium; Physical Chemistry; Symbolic Mathematics; Thermodynamics; Upper Division Undergraduate JCE Citation
Ferguson, Arthur. J. Chem. Educ. 2004, 81, 606.
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