AP Chemistry · Unit 9
Thermodynamics and Electrochemistry
In short
Unit 9: Thermodynamics and Electrochemistry in AP Chemistry covers 11 topics: Introduction to Entropy, Absolute Entropy and Entropy Change, Gibbs Free Energy and Thermodynamic Favorability, Thermodynamic and Kinetic Control and 7 more. Open each one for what you need to know, a self-check list and how it is tested on the exam.
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What is in Unit 9: Thermodynamics and Electrochemistry?
Unit 9: Thermodynamics and Electrochemistry
9.1 Introduction to Entropy
- I can explain how entropy increases when matter becomes more dispersed, such as during phase changes, volume increases, or reactions that produce a greater number of moles of gas.
- I can explain how entropy increases when energy is dispersed, using the kinetic molecular theory to relate an increase in temperature to a broader distribution of kinetic energy.
9.2 Absolute Entropy and Entropy Change
- I can use the equation ΔS°_reaction = ΣS°_products − ΣS°_reactants to calculate the entropy change for a process.
9.3 Gibbs Free Energy and Thermodynamic Favorability
- I can identify the standard state conditions for Gibbs free energy (pure substances, 1.0 M solutions, or gases at 1.0 atm/bar).
- I can use the term 'thermodynamically favored' for processes where ΔG° < 0 and avoid equating it with the rate of the reaction.
- I can calculate the standard Gibbs free energy change of a reaction using the standard Gibbs free energies of formation of the reactants and products.
- I can recognize situations where both enthalpy and entropy must be considered to determine if a process is thermodynamically favored.
- I can calculate ΔG° directly from the values of ΔH°, ΔS°, and temperature.
- I can predict the temperature conditions under which a process will be thermodynamically favored based on the signs of ΔH° and ΔS°, without needing to calculate ΔG° in certain cases.
9.4 Thermodynamic and Kinetic Control
9.5 Free Energy and Equilibrium
9.6 Free Energy of Dissolution
9.7 Coupled Reactions
9.8 Galvanic (Voltaic) and Electrolytic Cells
9.9 Cell Potential and Free Energy
- I can explain that thermodynamically favored redox reactions produce a positive voltage, while unfavored reactions produce a negative voltage and require an externally applied potential.
- I can calculate the standard cell potential of an electrochemical cell by identifying the oxidation and reduction half-reactions and their standard reduction potentials.
- I can use the equation ΔG° = −nFE° to relate standard cell potential to standard Gibbs free energy change, and use the sign of E° to determine if a reaction is thermodynamically favored.
9.10 Cell Potential Under Nonstandard Conditions
- I can explain that cell potential varies with the concentrations of active species and that the farther a reaction is from equilibrium, the greater the magnitude of the cell potential.
- I can state that Le Châtelier's principle does not apply to electrochemical systems because they are not in equilibrium.
- I can predict how deviations from standard conditions (Q = 1) change the magnitude of the cell potential relative to E°, and determine the direction of spontaneous electron flow in concentration cells.
- I can qualitatively use the Nernst equation to reason about the effects of concentration on cell potential without relying solely on algorithmic calculations.
9.11 Electrolysis and Faraday’s Law
- I can use Faraday’s laws to determine the stoichiometry of a redox reaction with respect to the number of electrons transferred, mass of material deposited/removed, current, time elapsed, and charge of ionic species.
Thermodynamics and Electrochemistry: common questions
What is in Unit 9: Thermodynamics and Electrochemistry?
It covers 11 topics: 9.1 Introduction to Entropy; 9.2 Absolute Entropy and Entropy Change; 9.3 Gibbs Free Energy and Thermodynamic Favorability; 9.4 Thermodynamic and Kinetic Control; 9.5 Free Energy and Equilibrium; 9.6 Free Energy of Dissolution; 9.7 Coupled Reactions; 9.8 Galvanic (Voltaic) and Electrolytic Cells; 9.9 Cell Potential and Free Energy; 9.10 Cell Potential Under Nonstandard Conditions; 9.11 Electrolysis and Faraday’s Law.
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