Unit 3 represents the first A2 modular assessment in the OxfordAQA International A-Level qualification. Building directly on the foundational principles established in AS Unit 1 and Unit 2, Unit 3 explores the energetic drivers of chemical reactions, electrochemical potentials, solution acid-base chemistry, and transition metal coordination complexes.
Unit 3 is examined in both the January series and the May/June series. Candidates typically sit Unit 3 in January of Year 13 as a modular milestone, allowing a resit opportunity in May/June to bank their highest UMS mark before final qualification cash-in (code 9622).
To achieve the final award of Grade A*, candidates must secure an overall Grade A across all 5 units (>= 400/500 total UMS) AND score at least 90% aggregate across the three A2 units (Units 3, 4, and 5). A commanding performance in Unit 3 provides essential headroom for the A* threshold.
Select a syllabus node below to access comprehensive revision notes, illustrated mechanisms, worked mathematical solutions, and exam-style practice questions:
Born-Haber energy cycles, lattice enthalpy of formation and dissociation, hydration and solution enthalpies, entropy (ΔS), Gibbs free energy feasibility (ΔG = ΔH − TΔS), and feasibility temperature calculations.
Open Topic Notes →Standard hydrogen electrode (SHE), IUPAC conventional cell notation, cell EMF calculations, thermodynamic redox feasibility, commercial lithium-ion batteries, and hydrogen-oxygen fuel cells.
Open Topic Notes →Complete acids-and-bases framework: Brønsted-Lowry pairs, Kw and water neutrality at elevated temperatures, weak acid Ka calculations, buffer action and buffer pH from Ka, and pH titration curves with indicator selection.
Open Topic Notes →Reactions of Na to S with water, oxygen and chlorine, structures and melting points of the oxides and chlorides, their reactions with water and pH, acid and anion structures, and amphoteric aluminium oxide.
Open Topic Notes →Transition metal properties, ligands and ligand substitution with colours, the chelate effect and haem, shapes and cis-trans and optical isomerism, and the origin of colour (ΔE = hν) with colorimetry.
Open Topic Notes →Vanadium oxidation states with zinc and acid, how pH and ligands change redox potentials, manganate(VII) titrations with worked calculations, and heterogeneous, homogeneous and autocatalysis.
Open Topic Notes →Comprehensive reactions-of-aqueous-ions: acidity differences between hexaaqua 2+ and 3+ ions, precipitation reactions with sodium hydroxide and ammonia, amphoteric dissolution of Al(OH)₃ in excess alkali, and reactions with sodium carbonate.
Open Topic Notes →Full written paper (80 marks) with AI marking, plus 15 warm-up multiple-choice questions.
Open Unit 3 Mock Exam →