AP Exam Prep · AP Chemistry
AP Chemistry Unit 9 Practice Test: Thermodynamics and Electrochemistry
Unit 9 asks whether a process is thermodynamically favourable and how that energy can be harnessed. You will use entropy, ΔG = ΔH − TΔS, the link between ΔG° and K, and electrochemical cells.
- Exam weighting:
- 7–9%
- Questions:
- 13 multiple choice
- Time:
- about 17 minutes
- Cost:
- Free, no sign-up
Taken this test before? Get a brand-new set of questions for this unit.
Question 1 of 13 · 0 answered
Jump to a question
You can change any answer before submitting.
What AP Chem Unit 9 covers
Unit 9, Thermodynamics and Electrochemistry, makes up 7–9% of the multiple-choice section and usually takes ~10–13 class periods. These are the topics in the current course framework, and every question in the test above is tagged with one of them.
- 9.1Introduction to Entropy
- 9.2Absolute Entropy and Entropy Change
- 9.3Gibbs Free Energy and Thermodynamic Favorability
- 9.4Thermodynamic and Kinetic Control
- 9.5Free Energy and Equilibrium
- 9.6Free Energy of Dissolution
- 9.7Coupled Reactions
- 9.8Galvanic (Voltaic) and Electrolytic Cells
- 9.9Cell Potential and Free Energy
- 9.10Cell Potential Under Nonstandard Conditions
- 9.11Electrolysis and Faraday's Law
Unit 9 key ideas
Entropy and free energy
Entropy increases with more gas particles, higher temperature and more dispersed matter. A process is thermodynamically favourable when ΔG = ΔH − TΔS is negative.
Favourable isn't always fast
A reaction can be favourable but too slow to observe if its activation energy is high; that's kinetic control.
ΔG° and K
ΔG° = −RT ln K, so a negative ΔG° means K > 1. Unfavourable reactions can be driven by coupling them to a favourable one.
Electrochemical cells
In a galvanic cell, oxidation happens at the anode and electrons flow to the cathode. E°cell = E°cathode − E°anode and ΔG° = −nFE°. Faraday's law links charge to moles of electrons.
Common Unit 9 mistakes
- Mixing kJ and J when combining ΔH and TΔS.
- Multiplying a standard reduction potential when scaling a half-reaction (potentials don't scale).
- Mixing up which electrode is the anode in galvanic and electrolytic cells.
How to study this unit
- Convert ΔS to kJ/K before using ΔG = ΔH − TΔS.
- For every cell, write both half-reactions, label anode and cathode, and show the direction of electron flow.
Need notes on a topic? Make one with the AI Study Guide Maker or turn it into flashcards.
More AP Chemistry practice tests
- Unit 1 · 7–9%Atomic Structure and Properties
- Unit 2 · 7–9%Compound Structure and Properties
- Unit 3 · 18–22%Properties of Substances and Mixtures
- Unit 4 · 7–9%Chemical Reactions
- Unit 5 · 7–9%Kinetics
- Unit 6 · 7–9%Thermochemistry
- Unit 7 · 7–9%Equilibrium
- Unit 8 · 11–15%Acids and Bases
- Unit 9 · 7–9%Thermodynamics and Electrochemistry
About these questions
StudyCoach wrote these questions for this test. Each one is mapped to a topic in the College Board's current AP Chemistry course framework. Every answer key was also checked by a separate AI review, and any disagreement was rechecked by hand. They have not yet been reviewed by an AP Chemistry teacher. If you think an answer is wrong, email support@studycoach.io.
AP® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, StudyCoach.