Chemistry II For Dummies
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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.

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John T. Moore, EdD, is regents professor of chemistry at Stephen F. Austin State University, where he teaches chemistry and is codirector of the Science, Technology, Engineering, and Mathematics (STEM) Research Center. He is the author of Biochemistry For Dummies and Chemistry For Dummies, 2nd Edition.

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