AP Exam Prep · AP Chemistry
AP Chemistry Unit 4 Practice Test: Chemical Reactions
Unit 4 is about writing, balancing and calculating with reactions. Most questions ask you to use a balanced equation's mole ratio, write a net ionic equation or classify a reaction.
- 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 4 covers
Unit 4, Chemical Reactions, makes up 7–9% of the multiple-choice section and usually takes ~14–15 class periods. These are the topics in the current course framework, and every question in the test above is tagged with one of them.
- 4.1Introduction for Reactions
- 4.2Net Ionic Equations
- 4.3Representations of Reactions
- 4.4Physical and Chemical Changes
- 4.5Stoichiometry
- 4.6Introduction to Titration
- 4.7Types of Chemical Reactions
- 4.8Introduction to Acid-Base Reactions
- 4.9Oxidation-Reduction (Redox) Reactions
Unit 4 key ideas
Balanced equations give mole ratios
Coefficients tell you how many moles react and form. Convert to moles, use the ratio, then convert back. The limiting reactant runs out first and sets the amount of product.
Net ionic equations show what changes
Split strong electrolytes into ions, cancel spectator ions, and keep solids, liquids, gases and weak electrolytes together.
Titration finds unknown amounts
At the equivalence point, moles of titrant match the stoichiometric amount of analyte, so the unknown concentration can be calculated.
Acid–base and redox
Brønsted–Lowry acids donate protons and bases accept them. In redox reactions, the species that loses electrons is oxidised and its oxidation number increases.
Common Unit 4 mistakes
- Using grams in a mole ratio instead of moles.
- Leaving spectator ions in a net ionic equation, or splitting a precipitate into ions.
- Mixing up which species is oxidised and which is the oxidising agent.
How to study this unit
- Use a three-step map for every stoichiometry problem: grams → moles → ratio → moles → grams.
- Memorise the common solubility rules and strong acids and bases so net ionic equations are quick.
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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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