AP Chemistry Study Guide

The course builds from the atom outward across nine units. It starts with atomic structure and properties (electron configuration, periodic trends, spectroscopy), then molecular and ionic compound structure and intermolecular forces and properties, which explain why substances have the melting points, solubilities, and behaviors they do.

The middle is reactions and rates: chemical reactions (types, stoichiometry, and titrations) and kinetics (how fast reactions go and the mechanisms behind them). The course closes with the energy and direction of change — thermodynamics (heat, enthalpy), equilibrium (reversible reactions and Le Châtelier's principle), acids and bases, and applications of thermodynamics (free energy and electrochemistry). The recurring idea is that structure determines properties, and energy plus entropy decide which way a reaction actually goes.

The College Board does not publish fixed percentage weights for the nine AP Chemistry units, so plan to be solid across all of them. The units are:

• Atomic Structure and Properties — configurations, periodic trends, PES
• Molecular and Ionic Compound Structure and Properties — bonding, Lewis structures
• Intermolecular Forces and Properties — phases, solutions, separations
• Chemical Reactions — types, stoichiometry, titration
• Kinetics — rate laws, mechanisms, catalysis
• Thermodynamics — enthalpy, calorimetry, Hess's law
• Equilibrium — $K$, ICE tables, Le Châtelier's principle
• Acids and Bases — pH, buffers, titration curves
• Applications of Thermodynamics — Gibbs free energy, electrochemistry

The practical takeaway: the early structure units feed everything after them, while equilibrium and acids/bases are the dense, high-leverage topics where many points — and many free-response questions — concentrate. Don't let the final thermodynamics/electrochemistry unit get squeezed out by end-of-year time pressure.

AP Chemistry rewards model-based reasoning supported by clean calculation. A routine that works:

1. Explain at the particle level. Many points come from describing why — why a bond is polar, why a rate increases — in terms of particles and forces, not just stating the outcome.
2. Drill the quantitative cores. Stoichiometry, ICE tables, pH and buffer math, and thermodynamic free-energy calculations recur constantly; speed and accuracy here free up time for reasoning.
3. Connect units deliberately. Equilibrium, acids/bases, and electrochemistry all reuse the same logic; studying them as one family is more efficient than treating each as new.
4. Work in mixed sets and review with full solutions. Mixed practice forces you to choose the right model, and reading a complete worked solution for a missed problem — including why a tempting wrong answer fails — teaches more than another easy one.

• Skipping the particle-level explanation. Stating that a substance has a high boiling point earns little without naming the specific intermolecular force responsible.
• Unit and significant-figure errors, or dropping the sign on enthalpy and free-energy values.
• Setting up ICE tables and equilibrium expressions wrong — forgetting to leave out pure solids and liquids, or mishandling the change row.
• Confusing strong vs. weak acids and bases in pH and titration problems, which throws off the entire curve.
• Vague free-response justifications. A correct number with no supporting reasoning, or a claim with no chemical mechanism, leaves easy points on the table.

Every unit below has a focused practice set with full written explanations and a rationale for every wrong choice, plus a worked-solutions page you can read straight through. Start with a unit you're shaky on, then take a mixed set across the whole subject to pressure-test your model selection before exam day. It's free and needs no account.