Tackling Thermodynamics Problems

By John T. Moore

Part of Chemistry II For Dummies Cheat Sheet

The Gibbs Free Energy is the best indicator about whether a reaction will be spontaneous or nonspontaneous. You’ll need to know this as you study Chemistry II. It has the form:


In this equation ΔG° is the Gibbs Free Energy of a reaction under standard conditions of 1 atm (or 1 bar) for gases and 1 M for solutions at 25°C; ΔH° is the enthalpy of the reaction under standard conditions; T is the Kelvin temperature; and ΔS° is the entropy of the reaction under standard conditions.

A spontaneous process has °G < 0. A nonspontaneous process has ΔG > 0. When °G = 0, the process is at equilibrium.