AP Exam Prep · AP Chemistry
AP Chemistry Unit 6 Practice Test: Thermochemistry
Unit 6 tracks energy in physical and chemical changes. You will calculate heat with q = mcΔT, find enthalpy changes from bond enthalpies, formation data and Hess's law, and read energy diagrams.
- Exam weighting:
- 7–9%
- Questions:
- 12 multiple choice
- Time:
- about 16 minutes
- Cost:
- Free, no sign-up
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What AP Chem Unit 6 covers
Unit 6, Thermochemistry, makes up 7–9% of the multiple-choice section and usually takes ~10–11 class periods. These are the topics in the current course framework, and every question in the test above is tagged with one of them.
- 6.1Endothermic and Exothermic Processes
- 6.2Energy Diagrams
- 6.3Heat Transfer and Thermal Equilibrium
- 6.4Heat Capacity and Calorimetry
- 6.5Energy of Phase Changes
- 6.6Introduction to Enthalpy of Reaction
- 6.7Bond Enthalpies
- 6.8Enthalpy of Formation
- 6.9Hess's Law
Unit 6 key ideas
Exothermic and endothermic
Exothermic processes release energy to the surroundings (ΔH < 0); endothermic processes absorb it (ΔH > 0). Breaking bonds always requires energy; forming bonds releases it.
Calorimetry
q = mcΔT. In a calorimeter, heat lost by one part equals heat gained by the other, so the temperature change of water can reveal the heat of a reaction.
Three ways to find ΔH
Use bond enthalpies (bonds broken − bonds formed), enthalpies of formation (products − reactants) or Hess's law (combine reactions, flipping signs and scaling as needed).
Phase changes
During melting or boiling, added energy overcomes intermolecular forces, so temperature stays constant until the change is complete.
Common Unit 6 mistakes
- Reversing the order in bond-enthalpy calculations (it's broken − formed).
- Forgetting to flip the sign when reversing a reaction in Hess's law, or to scale ΔH with coefficients.
- Mixing up the system and the surroundings when deciding the sign of q.
How to study this unit
- Write which way heat flows (system → surroundings or the reverse) before choosing a sign.
- Keep a one-line rule for each ΔH method and check which data the question gives you.
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.
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