Unit 2 · Spec 3.1.6
1. Kinetics, Collision Theory & Catalysis
Collision theory, activation energy, Maxwell-Boltzmann energy distributions with temperature changes, and catalysed reaction profiles.
Open Topic Notes →Unit Overview & Assessment Strategy
Unit 2 completes the AS modular tier. It examines quantitative physical chemistry (collision rates, equilibrium yields) and introduces systematic organic reaction mechanisms (curly arrow rules, carbocation intermediates, functional group transformations, and spectroscopic analysis). Unit 2 questions may also use amount of substance (3.1.2) and bonding (3.1.3) from Unit 1.
Examination Series & Windows
Unit 2 is examined in both the January series and the May/June series. Candidates typically sit Unit 1 in January and Unit 2 in May/June, or sit both together in May/June.
Modular Cash-In Flexibility
Unit 2 can be combined with Unit 1 to cash in the International AS award (code 9621), or retained as 20% of the composite score towards the full International A-Level award (code 9622).
OxfordAQA Examiner Differentiators in Unit 2
- Precise Curly Arrow Drawing: Curly arrows represent the movement of an electron pair. They must start directly from a lone pair of electrons or the exact centre of a covalent bond, and terminate precisely on the destination atom or between atoms to form a new bond.
- Carbocation Stability Explanations: Always quote the order of stability: tertiary > secondary > primary. Explain stability in terms of the positive inductive effect of electron-releasing alkyl groups dispersing the positive charge on the carbon atom.
- Mass Spectrometry [M+1] Peak (Beyond the OxfordAQA specification): The tiny peak one unit above the molecular ion peak is caused by the natural abundance of carbon-13 (1.1%), not an impurity.
- Atom Economy Balancing Coefficients: When calculating percentage atom economy, remember to multiply the Mr of each substance by its stoichiometric balancing coefficient from the balanced equation: (% atom economy = [sum of (coefficient * Mr of desired product)] / [sum of (coefficient * Mr of all reactants)] * 100).
- Addition vs Condensation Polymers: Addition polymerisation forms a single polymer product with 100% atom economy by opening C=C double bonds. In contrast, condensation polymerisation eliminates a small molecule (such as H₂O or HCl) and can use either two different difunctional monomers (e.g. dicarboxylic acid + diol/diamine) or a single bifunctional monomer (e.g. an amino acid or hydroxycarboxylic acid).
Unit 2 Syllabus Topics (9 Modules)
Select any module below to access comprehensive revision notes, step-by-step mechanism guides, worked examples, and interactive practice questions:
Unit 2 · Spec 3.1.7
2. Dynamic Equilibria & Equilibrium Constant Kc
Dynamic equilibrium, Le Chatelier's principle, homogeneous Kc expressions, ICE calculation tables, and temperature dependence of Kc.
Open Topic Notes →Unit 2 · Spec 3.3.1
3. Introduction to Organic Chemistry
Six types of formula, homologous series, IUPAC naming, curly arrows and radicals, structural isomers, and E-Z isomerism with CIP rules.
Open Topic Notes →Unit 2 · Spec 3.3.2
4. Alkanes & Free-Radical Substitution
Crude oil fractional distillation, thermal vs catalytic cracking, complete/incomplete combustion, and free-radical chlorination mechanism.
Open Topic Notes →Unit 2 · Spec 3.3.3
5. Halogenoalkanes: Nucleophilic Substitution & Elimination
Bond polarity and reactivity, curly arrow precision, nucleophilic substitution with OH⁻, CN⁻, NH₃, base elimination, and ozone depletion by chlorine radicals (beyond the specification).
Open Topic Notes →Unit 2 · Spec 3.3.4.1 to 3.3.4.3
6. Alkenes: Structure, Electrophilic Addition & Polymers
Double bond structure and E/Z isomerism, electrophilic addition mechanisms (HBr, H₂SO₄, Br₂), carbocation stability, Markovnikov rule, and addition polymers.
Open Topic Notes →Unit 2 · Spec 3.3.4.4
7. Epoxyethane
Partial oxidation of ethene and its hazards, ring strain, reactions with water and alcohols, the ring-opening mechanism, antifreeze and surfactants.
Open Topic Notes →Unit 2 · Spec 3.3.5
8. Alcohols: Oxidation, Elimination and Tests
Classification of alcohols, oxidation of primary, secondary and tertiary alcohols with acidified dichromate, elimination (dehydration) to alkenes, and chemical tests.
Open Topic Notes →Unit 2 · Spec 3.3.6
9. Organic Analysis: Infrared Spectroscopy & Mass Spectrometry
Infrared absorption wavenumber ranges (O-H, C=O), fingerprint region, mass spectrometry molecular ion M⁺ peaks, and chemical test summaries.
Open Topic Notes →
Mock Exam Practice
Start Unit 2 Exam Practice →
Unit 2 Mock Examination
Full written paper (70 marks) with AI marking, plus 15 warm-up multiple-choice questions.