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Chem

AP Chemistry

General chemistry from atoms to electrochemistry, drilled on the particle diagrams, data tables, and calculations the exam is built from.

Category
Sciences
Units
9 units
Exam
Exam May 6, 2027 (in 221 days)
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Unit 1 is free with an account. No card, no trial clock.

What the course covers

A full year of college general chemistry in nine units: atomic structure and periodicity, bonding and molecular shape, intermolecular forces, gases and solutions, reactions and stoichiometry, kinetics, thermochemistry, equilibrium, acids and bases, and thermodynamics with electrochemistry. Every unit trains what AP readers actually score: calculations with units and significant figures (the largest single share of both sections), particle-level reasoning that connects a diagram to a macroscopic observation, experimental design and error analysis from lab scenarios, and claim, evidence, and reasoning justifications built on Coulomb's law, intermolecular forces, QQ versus KK, and ΔG∘\Delta G^\circ. The exam is 60 four-choice multiple-choice questions and 7 free-response questions (3 ten-point long answers and 4 four-point short answers), with a calculator, the periodic table, and the equations and constants sheet available throughout.

9 units, with exam weights

  1. Unit 1

    Atomic Structure and Properties

    7-9% of examFree
    Counting particles by weighing: the mole, molar mass, isotopes and mass spectra, and composition by mass for pure substances and mixtures. Then the atom itself: electron configurations, photoelectron spectroscopy, and periodic trends explained with Coulomb's law, shielding, and effective nuclear charge.
    8 topics
    1. 1.1Moles and Molar Mass
    2. 1.2Mass Spectra of Elements
    3. 1.3Elemental Composition of Pure Substances
    4. 1.4Composition of Mixtures
    5. 1.5Atomic Structure and Electron Configuration
    6. 1.6Photoelectron Spectroscopy
    7. 1.7Periodic Trends
    8. 1.8Valence Electrons and Ionic Compounds

  2. Unit 2

    Compound Structure and Properties

    7-9% of exam
    How atoms hold together and what shape they take: ionic, covalent, and metallic bonding, the potential energy curve of a bond, ionic and metallic solids and alloys, Lewis diagrams with resonance and formal charge, and VSEPR geometry, polarity, and hybridization.
    7 topics
    1. 2.1Types of Chemical Bonds
    2. 2.2Intramolecular Force and Potential Energy
    3. 2.3Structure of Ionic Solids
    4. 2.4Structure of Metals and Alloys
    5. 2.5Lewis Diagrams
    6. 2.6Resonance and Formal Charge
    7. 2.7VSEPR and Hybridization

  3. Unit 3

    Properties of Substances and Mixtures

    18-22% of exam
    The heaviest unit on the exam. Intermolecular and interparticle forces explain the properties of solids, liquids, and solutions; the ideal gas law, kinetic molecular theory, and real-gas deviations describe gases; molarity, particle views of solutions, chromatography, and solubility describe mixtures; and photons, spectroscopy, and the Beer-Lambert law connect light to structure and concentration.
    13 topics
    1. 3.1Intermolecular and Interparticle Forces
    2. 3.2Properties of Solids
    3. 3.3Solids, Liquids, and Gases
    4. 3.4Ideal Gas Law
    5. 3.5Kinetic Molecular Theory
    6. 3.6Deviation from Ideal Gas Law
    7. 3.7Solutions and Mixtures
    8. 3.8Representations of Solutions
    9. 3.9Separation of Solutions and Mixtures
    10. 3.10Solubility
    11. 3.11Spectroscopy and the Electromagnetic Spectrum
    12. 3.12Properties of Photons
    13. 3.13Beer-Lambert Law

  4. Unit 4

    Chemical Reactions

    7-9% of exam
    Representing and quantifying change: evidence of physical and chemical change, balanced molecular and net ionic equations, particle diagrams of reactions, stoichiometry with limiting reactants, titration, and the three reaction types the course uses: acid-base (Brønsted-Lowry), precipitation, and oxidation-reduction.
    9 topics
    1. 4.1Introduction for Reactions
    2. 4.2Net Ionic Equations
    3. 4.3Representations of Reactions
    4. 4.4Physical and Chemical Changes
    5. 4.5Stoichiometry
    6. 4.6Introduction to Titration
    7. 4.7Types of Chemical Reactions
    8. 4.8Introduction to Acid-Base Reactions
    9. 4.9Oxidation-Reduction (Redox) Reactions

  5. Unit 5

    Kinetics

    7-9% of exam
    How fast reactions go and why: rates and rate laws from initial-rate and concentration-time data, integrated rate laws and half-life, the collision model and energy profiles, mechanisms with rate-limiting and pre-equilibrium steps, and catalysis.
    11 topics
    1. 5.1Reaction Rates
    2. 5.2Introduction to Rate Law
    3. 5.3Concentration Changes Over Time
    4. 5.4Elementary Reactions
    5. 5.5Collision Model
    6. 5.6Reaction Energy Profile
    7. 5.7Introduction to Reaction Mechanisms
    8. 5.8Reaction Mechanism and Rate Law
    9. 5.9Pre-Equilibrium Approximation
    10. 5.10Multistep Reaction Energy Profile
    11. 5.11Catalysis

  6. Unit 6

    Thermochemistry

    7-9% of exam
    Energy in physical and chemical change: endothermic and exothermic processes and energy diagrams, heat transfer and thermal equilibrium, calorimetry, phase-change energy, enthalpy of reaction, bond enthalpies, enthalpies of formation, and Hess's law.
    9 topics
    1. 6.1Endothermic and Exothermic Processes
    2. 6.2Energy Diagrams
    3. 6.3Heat Transfer and Thermal Equilibrium
    4. 6.4Heat Capacity and Calorimetry
    5. 6.5Energy of Phase Changes
    6. 6.6Introduction to Enthalpy of Reaction
    7. 6.7Bond Enthalpies
    8. 6.8Enthalpy of Formation
    9. 6.9Hess's Law

  7. Unit 7

    Equilibrium

    7-9% of exam
    Reversible reactions that reach a dynamic balance: writing Q and K, calculating K and equilibrium concentrations with ICE tables, the meaning of large and small K, manipulating K for combined reactions, particle views of equilibrium, Le Châtelier's principle and Q versus K, and solubility equilibria with Ksp and the common-ion effect.
    12 topics
    1. 7.1Introduction to Equilibrium
    2. 7.2Direction of Reversible Reactions
    3. 7.3Reaction Quotient and Equilibrium Constant
    4. 7.4Calculating the Equilibrium Constant
    5. 7.5Magnitude of the Equilibrium Constant
    6. 7.6Properties of the Equilibrium Constant
    7. 7.7Calculating Equilibrium Concentrations
    8. 7.8Representations of Equilibrium
    9. 7.9Introduction to Le Châtelier's Principle
    10. 7.10Reaction Quotient and Le Châtelier's Principle
    11. 7.11Introduction to Solubility Equilibria
    12. 7.12Common-Ion Effect

  8. Unit 8

    Acids and Bases

    11-15% of exam
    The second-heaviest unit: pH and pOH with Kw, strong and weak acids and bases with Ka and Kb, reactions of acid-base mixtures, titration curves and the half-equivalence point, acid strength from molecular structure, indicators and predominant forms, buffers with Henderson-Hasselbalch and buffer capacity, and the effect of pH on solubility.
    11 topics
    1. 8.1Introduction to Acids and Bases
    2. 8.2pH and pOH of Strong Acids and Bases
    3. 8.3Weak Acid and Base Equilibria
    4. 8.4Acid-Base Reactions and Buffers
    5. 8.5Acid-Base Titrations
    6. 8.6Molecular Structure of Acids and Bases
    7. 8.7pH and pKa
    8. 8.8Properties of Buffers
    9. 8.9Henderson-Hasselbalch Equation
    10. 8.10Buffer Capacity
    11. 8.11pH and Solubility

  9. Unit 9

    Thermodynamics and Electrochemistry

    7-9% of exam
    Why reactions happen: entropy, Gibbs free energy and thermodynamic favorability, kinetic versus thermodynamic control, the link between ΔG∘\Delta G^\circ and K, the free energy of dissolution, coupled reactions, then galvanic and electrolytic cells, cell potential and free energy, nonstandard conditions, and electrolysis with Faraday's law.
    11 topics
    1. 9.1Introduction to Entropy
    2. 9.2Absolute Entropy and Entropy Change
    3. 9.3Gibbs Free Energy and Thermodynamic Favorability
    4. 9.4Thermodynamic and Kinetic Control
    5. 9.5Free Energy and Equilibrium
    6. 9.6Free Energy of Dissolution
    7. 9.7Coupled Reactions
    8. 9.8Galvanic (Voltaic) and Electrolytic Cells
    9. 9.9Cell Potential and Free Energy
    10. 9.10Cell Potential Under Nonstandard Conditions
    11. 9.11Electrolysis and Faraday's Law

The exam, part by part

3 parts, 3 h 15 min in all.

  • Section I: Multiple Choice

    Questions
    60
    Time
    1 h 30 min
    Weight
    50%

    Calculator allowed

    Format details

    Sixty questions, four answer choices (A-D), answered on screen in Bluebook. A mix of discrete items and sets of 2-5 items that share one stimulus (a data table, graph, particle diagram, lab description, or chemical equation). Choice formats are text, diagrams, chemical equations, or numerical expressions. Unit weights on this section: Units 1, 2, 4, 5, 6, 7, 9 at 7-9% each; Unit 3 at 18-22%; Unit 8 at 11-15%. Practice weights: Mathematical Routines 35-42%, Model Analysis 23-30%, Models and Representations, Question and Method, and Argumentation 8-12% each; Representing Data and Phenomena is not assessed in multiple choice.

  • Section II: Long Free Response (Questions 1-3)

    Questions
    3
    Time
    1 h 9 min
    Weight
    32.6%

    Calculator allowed

    Format details

    Task types: Long Answer

    Three 10-point multipart questions, about 23 minutes each (suggested pacing; Section II is one 105-minute block and students may move between questions). Questions are shown in Bluebook and answered by hand in a paper booklet, in parts labeled A, B, C... with sub-parts i, ii, iii. In every recent year (2023-2026) at least one long question has been built on a laboratory experiment with data. Weight shown is this part's share of the 46 free-response points (30 of 46) within the 50% section.

  • Section II: Short Free Response (Questions 4-7)

    Questions
    4
    Time
    36 min
    Weight
    17.4%

    Calculator allowed

    Format details

    Task types: Short Answer

    Four 4-point multipart questions, about 9 minutes each, in the same 105-minute block. Each short question focuses on one or two topics (for example bonding and intermolecular forces, a Ksp or Kp calculation, a spectrophotometry or calorimetry experiment, a galvanic cell). Weight shown is this part's share of the 46 free-response points (16 of 46) within the 50% section.

How the 1 to 5 score is set

Section I (60 multiple-choice questions, one point each, no penalty for wrong answers) and Section II (46 free-response points: three 10-point long questions and four 4-point short questions) each count for 50% of the composite. Free-response points are awarded row by row, each row one point tied to one specific piece of work (a correct calculated value with setup shown, an equation, a drawing, or a claim with a valid justification); later parts are scored consistently with an earlier wrong answer where the method is right. Some calculation rows also require correct significant figures, units, or sign, and the scoring guideline says so for that row. The weighted composite is converted to the 1-5 AP scale using cut scores set each year (2025: 17.8% of students earned a 5, mean score 3.36).

What you bring and get

Students have the AP Chemistry periodic table and the AP Chemistry Equations and Constants sheet (effective 2025) for the entire exam, in print and in Bluebook. A scientific or graphing calculator is permitted on both sections (a four-function calculator is allowed but not recommended), and Bluebook provides built-in Desmos scientific and graphing calculators. No table of reduction potentials, bond enthalpies, enthalpies of formation, entropies, Ka values, or solubility rules is provided: any such values a question needs are given in the question. The exam is hybrid digital: multiple choice is answered in Bluebook; free-response questions are shown in Bluebook and answered by hand in a paper booklet, where students must show their work and attend to significant figures.

Skills the exam scores

  • SP1Models and Representations

    Describe models and representations across scales: read the components and quantitative information in particle-level models (1.A) and in models that show both particle-level and macroscopic properties (1.B). Exam weight: 8-12% of multiple choice, 2-4% of free response.

  • SP2Question and Method

    Determine scientific questions and methods: identify a testable question (2.A), form a hypothesis or predict results (2.B), choose procedures that fit the question, including sketching a lab setup (2.C), collect data from lab representations with attention to precision (2.D), name sources of experimental error (2.E), and explain how changing a procedure changes the results (2.F). Exam weight: 8-12% of multiple choice, 10-16% of free response.

  • SP3Representing Data and Phenomena

    Create representations: graph data with correct scale and units (3.A), draw chemical substances or phenomena with appropriate diagrams such as Lewis diagrams, electron configurations, or particle views (3.B), and show visually how structure and interactions connect across scales (3.C). Assessed only in free response (8-16%).

  • SP4Model Analysis

    Analyze and interpret models: explain or predict properties and phenomena with given theories and models (4.A), judge whether a model is consistent with chemical theory (4.B), connect particle-level and macroscopic properties (4.C), and explain how well a representation captures that connection (4.D). Exam weight: 23-30% of multiple choice, 5-9% of free response.

  • SP5Mathematical Routines

    Solve problems with mathematical relationships: pick out the needed quantities from text, tables, or graphs (5.A), choose the right relationship (5.B), explain how variables in an equation relate when one changes (5.C), read information from graphs (5.D), write a balanced equation for a phenomenon (5.E), and calculate or estimate an unknown by a logical pathway with dimensional analysis and significant figures (5.F). The largest practice: 35-42% of multiple choice, 43-53% of free response.

  • SP6Argumentation

    Develop an explanation or scientific argument: make a claim (6.A), support it with experimental data (6.B) or with particle-level representations such as atomic and molecular structure (6.C), justify it with chemical principles or mathematical reasoning (6.D) or with connections between particle and macroscopic scales (6.E), connect experimental results to chemical concepts (6.F), and explain how sources of error affect results (6.G). Exam weight: 8-12% of multiple choice, 15-24% of free response.