AP Chemistry covers 9 units of college-level chemistry. About 17% of students score a 5 (College Board recalibrated the exam in 2025). The exam is 60 MCQs (50%) and 7 FRQs (50%). FRQs reward clear, mechanistic explanations written at the particle level — vague answers score zero even if the idea is correct.
Unit 1: Atomic Structure and Properties (7–9%)
Electron configuration, periodic trends (atomic radius, ionization energy, electronegativity), and the quantum mechanical model. Know how to predict electron configuration for ions and excited states. Periodic trends appear in 3–4 MCQs every exam.
Unit 2: Molecular and Ionic Compound Structure (7–9%)
Lewis structures, VSEPR theory, bond polarity, and molecular geometry. Know how to predict shape and polarity for any molecule. Intermolecular forces (London dispersion, dipole-dipole, hydrogen bonding) determine physical properties and appear on both MCQ and FRQ.
Unit 3: Intermolecular Forces and Properties (18–22%)
The highest-weight unit. Solid and liquid properties, vapor pressure, and colligative properties (boiling point elevation, freezing point depression, osmotic pressure). Chromatography and spectroscopy concepts. Understand how IMFs explain observable physical properties — this is a common FRQ connection question.
Unit 4: Chemical Reactions (7–9%)
Reaction types, net ionic equations, and solubility rules. Oxidation-reduction reactions and balancing redox equations (half-reaction method). Know the 7 strong acids and 8 strong bases — every acid-base calculation depends on correctly identifying them.
Unit 5: Kinetics (7–9%)
Rate laws (first, second, zero order), integrated rate laws, half-life, and reaction mechanisms. The rate-determining step concept is heavily tested: given a mechanism, identify which step's molecularity determines the overall rate law. Arrhenius equation connects activation energy to rate.
Unit 6: Thermodynamics (7–9%)
ΔH (enthalpy), ΔS (entropy), ΔG (Gibbs free energy). Hess's Law for calculating ΔH of reactions. Know the four ΔG = ΔH − TΔS cases and when spontaneity depends on temperature vs. when it's temperature-independent.
Unit 7: Equilibrium (7–9%)
Equilibrium constant expressions (K, Kp, Kc), reaction quotient Q, ICE tables, and Le Chatelier's principle. Solubility product Ksp and common ion effect. The connection between ΔG and K (ΔG° = −RT ln K) appears in FRQs that bridge Units 6 and 7.
Unit 8: Acids and Bases (11–15%)
The most heavily tested unit. Strong vs. weak acid/base calculations, Ka/Kb, pH, pOH, buffer systems, and Henderson-Hasselbalch equation (pH = pKa + log([A⁻]/[HA])). Acid-base titrations and interpreting titration curves — especially the equivalence point and buffer region. Polyprotic acids are a common FRQ topic.
Unit 9: Electrochemistry (7–9%)
Galvanic (voltaic) vs. electrolytic cells, cell potential (E°cell), Nernst equation, and Faraday's Law. Know how to calculate E°cell from standard reduction potentials and predict whether a reaction is spontaneous. The connection between E°cell and ΔG (ΔG = −nFE) rounds out the thermodynamic connections tested across Units 6, 7, and 9.
FRQ Writing Tips
- Always justify at the particle/molecular level — say WHY in terms of bonds, forces, or electron behavior
- Write balanced equations — unbalanced equations score zero for that part
- Show all calculation steps with units
- For FRQs asking you to predict and explain: predict first, then explain the reason
AP Chemistry Practice Questions · AP Chem Practice Test · How to Get a 5 on AP Chem
AP and Advanced Placement are trademarks of College Board. AimFive is not affiliated with or endorsed by College Board.
