AP®︎ Chemistry: Topic 9.3 Flashcards

Master key terms and definitions for Topic 9.3 of AP Chemistry – Gibbs Free Energy and Thermodynamic Favorability to help you prep for quizzes and the AP exam.

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Term

Standard Gibbs Free Energy Change (ΔG°)

Definition

The free energy change for a process when all substances are in standard states.

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Standard Gibbs Free Energy Change (ΔG°)
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The free energy change for a process when all substances are in standard states.

9.3.A9.3.A.1
Standard Gibbs Free Energy of Formation (ΔGf°)
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The free energy change when one mole of a compound forms from elements in standard states.

9.3.A9.3.A.3
Calculating ΔG°reaction from ΔGf° Values
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Add product formation values, subtract reactant formation values, and include stoichiometric coefficients.

9.3.A9.3.A.3
ΔGf° of Elements in Standard States
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Any element in its standard state has a formation free energy of zero.

9.3.A9.3.A.3
Exergonic vs. Endergonic
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Exergonic processes have ΔG° < 0; endergonic processes have ΔG° > 0.

9.3.A9.3.A.2
Freezing of Water and Thermodynamic Favorability
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Exothermic and entropy-decreasing, so it is favored only at low temperatures.

9.3.A9.3.A.4
Dissolution of Sodium Nitrate and Thermodynamic Favorability
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Endothermic but entropy-increasing, so it can be favored at sufficiently high temperatures.

9.3.A9.3.A.4
Thermodynamically Favored vs. Spontaneous
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A process with ΔG° < 0 is thermodynamically favored, historically called spontaneous.

9.3.A9.3.A.2
Gibbs Free Energy and Sign Rules
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Free energy equals ΔH° − TΔS°, so ΔH° and ΔS° signs predict favorability.

9.3.A9.3.A.5