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Units group related chemistry topics and can contain several course levels. Follow a suggested lesson selection or open any unit directly. Course placement is separate from question difficulty.

14 units available with 1550 practice questions.

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Unit 01Levels vary by lesson
Stoichiometry
Convert between mass, moles, and particles; balance equations; and calculate limiting reagents, percent composition, empirical formulas, and percent yield.
Course level: FoundationsCourse level: High School / HonorsCourse level: AP Chemistry
Limiting ReagentsEmpirical FormulasLab: Hydrate Analysis & Gravimetric Thermal DecompositionBalancing Chemical EquationsThe Mole & Mole Conversions
Questions
158
Topics
8
Difficulty
Easy · Medium · Hard
Example question · Easy
Why must a porcelain crucible be heated strongly and cooled in a desiccator before adding a hydrated salt sample in a gravimetric hydrate analysis lab? Formulas of named substances: water = H₂O.
View unit: View Stoichiometry unit
Unit 02Levels vary by lesson
Periodic Trends
Explain atomic radius, ionization energy, and electronegativity trends using electron configuration, shielding, and effective nuclear charge.
Course level: High School / HonorsCourse level: AP Chemistry
Shielding & Electron Orbital StructureElectronegativity, Ionization Energy & Atomic Radius
Questions
75
Topics
2
Difficulty
Easy · Medium · Hard
Example question · Easy
Which statement correctly compares the atomic radii of potassium and calcium?
View unit: View Periodic Trends unit
Unit 03Levels vary by lesson
Types of Solids and IMFs
Identify intermolecular forces and types of solids, and use them to justify differences in physical properties and chromatography results.
Course level: FoundationsCourse level: High School / HonorsCourse level: AP Chemistry
Lab: Paper & Thin-Layer Chromatography of DyesSolidsJustifying Properties with IMFsTypes of ElementsIntroduction to IMFs
Questions
116
Topics
5
Difficulty
Easy · Medium · Hard
Example question · Easy
Which of the following elements is classified as a semiconductor metalloid?
View unit: View Types of Solids and IMFS unit
Unit 04Levels vary by lesson
Lewis Structures & Formal Charge
Draw Lewis structures, apply the octet rule and its exceptions, and use formal charge to choose the best structure.
Course level: FoundationsCourse level: High School / HonorsCourse level: AP Chemistry
Formal ChargeLewis StructuresOctet Rule
Questions
74
Topics
3
Difficulty
Easy · Medium · Hard
Example question · Easy
What is the total number of valence electrons in the Lewis structure of the ammonium cation, NH₄⁺?
View unit: View Molecular Structure unit
Unit 05Levels vary by lesson
Molecular Geometry & Bonding (VSEPR)
Predict VSEPR shapes, assign hybridization, and count sigma and pi bonds from a molecule's electron domains.
Course level: High School / HonorsCourse level: AP ChemistryCourse level: College Extension
VSEPRSigma and Pi BondsHybridizationElectron Orbitals
Questions
97
Topics
4
Difficulty
Easy · Medium · Hard
Example question · Easy
What is the molecular geometry of carbon tetrachloride (CCl₄)?
View unit: View Bonding unit
Unit 06Levels vary by lesson
Gases, Solutions & Spectroscopy
Apply the ideal gas law, Dalton's law, and kinetic molecular theory; describe solutions and chromatography; and use Beer's law to find concentration.
Course level: High School / HonorsCourse level: AP ChemistryCourse level: College Extension
Ideal Gas Law, Dalton's Law & Gas StoichiometrySpectroscopy & Beer-Lambert LawGraham's Law of Effusion & van der Waals EquationKinetic Molecular Theory & Speed DistributionsSolutions, Mixtures & Chromatography
Questions
117
Topics
6
Difficulty
Easy · Medium · Hard
Example question · Easy
According to the Beer-Lambert Law (A = ε · b · c), what is the relationship between absorbance (A) and path length (b) of the sample cuvette?
View unit: View Gases, Solutions & Spectroscopy unit
Unit 07Levels vary by lesson
Chemical Reactions
Write net ionic equations, assign oxidation numbers, balance redox reactions, and solve solution stoichiometry, titration, and gravimetric problems.
Course level: High School / HonorsCourse level: AP Chemistry
Acid-Base Neutralization & Proton TransferSolution Stoichiometry & Gravimetric AnalysisNet Ionic Equations & Precipitation ReactionsOxidation Numbers & Identifying Redox ReactionsLab: Gravimetric Analysis of Precipitation
Questions
145
Topics
7
Difficulty
Easy · Medium · Hard
Example question · Easy
In a gravimetric analysis to determine the sulfate content of an unknown fertilizer, which soluble reagent is added in excess to precipitate all sulfate quantitatively as an insoluble solid?
View unit: View Chemical Reactions unit
Unit 08Levels vary by lesson
Chemical Kinetics
Determine rate laws from data, use integrated rate laws and half-life, relate mechanisms to rate laws, and apply collision theory and the Arrhenius equation.
Course level: High School / HonorsCourse level: AP ChemistryCourse level: College Extension
Collision Theory & Arrhenius EquationIntegrated Rate Laws & Half-LifeReaction Rates & Differential Rate LawsElementary Steps & Reaction Mechanisms
Questions
123
Topics
4
Difficulty
Easy · Medium · Hard
Example question · Easy
If a reaction rate is independent of the concentration of reactant A, what is the order with respect to A?
View unit: View Chemical Kinetics unit
Unit 09Levels vary by lesson
Thermochemistry & Thermodynamics
Calculate heat with calorimetry, Hess's law, enthalpies of formation, and bond energies, and judge thermodynamic favorability with entropy and Gibbs free energy.
Course level: FoundationsCourse level: High School / HonorsCourse level: AP Chemistry
Heat Transfer, Specific Heat & CalorimetryHess's Law & Standard Enthalpies of FormationBond Dissociation Energies & Enthalpy of ReactionEntropy, Gibbs Free Energy & Thermodynamic FavorabilityLab: Coffee-Cup Calorimetry & Heat of Reaction
Questions
132
Topics
5
Difficulty
Easy · Medium · Hard
Example question · Easy
What is the heat absorbed by 200.0 g of water (H₂O) (c = 4.184 J/g°C) when heated by 10.0 °C?
View unit: View Thermochemistry & Thermodynamics unit
Unit 10Levels vary by lesson
Chemical Equilibrium & Solubility
Write K and Q expressions, solve ICE tables, predict Le Chatelier shifts, and calculate solubility with Ksp and the common-ion effect.
Course level: High School / HonorsCourse level: AP Chemistry
Solubility Product Ksp & Common Ion EffectEquilibrium Constant & Reaction Quotient Q vs KLe Chatelier's Principle & System ShiftsICE Tables & Equilibrium CalculationsLab: Spectrophotometric Equilibrium Constant Determination
Questions
132
Topics
5
Difficulty
Easy · Medium · Hard
Example question · Easy
In the lab determining the equilibrium constant for Fe³⁺(aq) + SCN⁻(aq) ⇌ [Fe(SCN)]²⁺(aq), what visible property is used to quantify the equilibrium concentration of the product?
View unit: View Chemical Equilibrium & Solubility unit
Unit 11Levels vary by lesson
Acids, Bases & Aqueous Equilibria
Calculate pH for strong and weak acids and bases, design and analyze buffers, and interpret titration curves and indicators.
Course level: High School / HonorsCourse level: AP Chemistry
Acid-Base Titration Curves & Chemical IndicatorsBuffer Solutions & Henderson-Hasselbalch EquationpH, pOH, Kw & Strong Acid-Base CalculationsWeak Acids, Weak Bases, Ka/Kb & Salt Hydrolysis
Questions
122
Topics
4
Difficulty
Easy · Medium · Hard
Example question · Easy
What is the pH of a 0.0010 M HCl solution at 25 °C?
View unit: View Acids, Bases & Aqueous Equilibria unit
Unit 12Levels vary by lesson
Electrochemistry & Applications of Thermodynamics
Calculate cell potentials from reduction potentials, connect E°, ΔG°, and K, apply the Nernst equation, and solve Faraday's law electrolysis problems.
Course level: High School / HonorsCourse level: AP ChemistryCourse level: College Extension
Electrolytic Cells & Faraday's Law CalculationsGalvanic Cells & Standard Reduction PotentialsCell Potential, Gibbs Free Energy & Equilibrium ConstantNernst Equation & Concentration Cells
Questions
123
Topics
4
Difficulty
Easy · Medium · Hard
Example question · Easy
In an electrochemical cell, which process occurs at the ANODE?
View unit: View Electrochemistry & Applications of Thermodynamics unit
Unit 13Levels vary by lesson
Organic Chemistry
Name hydrocarbons with IUPAC rules, recognize functional groups, distinguish structural isomers and stereoisomers, and classify basic organic reactions.
Course level: High School / HonorsCourse level: College Extension
Structural Isomerism & StereochemistryOrganic Reactions: Substitution, Addition & CombustionFunctional Groups & Organic FamiliesHydrocarbons & IUPAC Nomenclature
Questions
68
Topics
4
Difficulty
Easy · Medium
Example question · Easy
What is the general molecular formula for an acyclic (open-chain) alkane containing n carbon atoms?
View unit: View Organic Chemistry unit
Unit 14Levels vary by lesson
Nuclear Chemistry
Balance nuclear equations, calculate half-life and decay, relate mass defect to binding energy, and compare fission and fusion.
Course level: High School / HonorsCourse level: College Extension
Nuclear Decay & Balancing Nuclear EquationsHalf-Life & Radioactive Decay KineticsMass Defect, Binding Energy & E = mc²Fission, Fusion & Nuclear Energy
Questions
68
Topics
4
Difficulty
Easy · Medium · Hard
Example question · Easy
An alpha particle is identical to a:
View unit: View Nuclear Chemistry unit