QCE Chemistry: complete 2026 guide to Units 3 and 4 (General subject)
A complete 2026 guide to QCE General Chemistry Units 3 and 4. The IA1 data test, IA2 student experiment, IA3 research investigation and External Assessment structure, what each instrument assesses, how marks combine into your subject result, and links to every dot-point answer we have for QCE Chemistry across Units 1 to 4.
QCE General Chemistry Units 3 and 4 is the Year 12 sequence assessed across three internal assessments (IAs) and one External Assessment (EA). Unit 3 (Equilibrium, acids and redox reactions) is the priority for IA1 and IA2, both sat during the unit. The EA tests Units 3 and 4 cumulatively at the end of the year.
This page is the index. Below you will find the structure of the course, what each instrument assesses, and links to every dot-point answer we have written for QCE Chemistry Unit 3.
The four instruments in 2026
IA1: Data test. A school-based 60 to 90-minute response to previously unseen Unit 3 data sets (equilibrium tables, titration curves, reduction-potential data). Tests claim-evidence-reasoning under time pressure. 10 percent of the subject result. Sat early in Term 1 or Term 2 of Year 12.
IA2: Student experiment. A student-designed and conducted experimental investigation drawn from Unit 3 subject matter (commonly equilibrium shifts, acid-base titrations, or galvanic cells). Reported as a scientific report of up to 2000 words. 20 percent of the subject result.
IA3: Research investigation. A research-only investigation in Unit 4 context, examining a claim by reviewing secondary data. Reported as a scientific article of up to 2000 words. 20 percent of the subject result.
EA: External Assessment. Two centrally-set exam papers at the end of Unit 4. Paper 1 is multiple choice plus short response (60 marks). Paper 2 is extended response and data analysis (60 marks). 50 percent of the subject result.
Unit 3: Equilibrium, acids and redox reactions
Unit 3 splits into two topics. Both are examinable in IA1 and the EA; most IA2 experiments are designed around one of them.
Topic 1: Chemical equilibrium systems. Reversible reactions and dynamic equilibrium. The equilibrium law and Kc. Le Chatelier's principle. Industrial equilibria (Haber, Contact). Bronsted-Lowry acids and bases. Strong and weak acids. pH and Kw. Buffer systems.
Topic 2: Oxidation and reduction. Oxidation numbers. Construction of half-equations. The standard reduction potential table. Galvanic cells (anode, cathode, salt bridge, cell potential). Electrolytic cells and Faraday's laws. Redox in corrosion and electroplating.
Our 2026 QCE Chemistry dot-point answers
Every link below is a focused answer to one QCAA subject-matter dot point. Each page identifies the dot point, gives the worked answer, cites past QCAA-style questions where available, and cross-links to related dot points.
Unit 1 (foundational, not assessed by IA but examined in the EA)
Unit 1 (Chemical fundamentals: structure, properties and reactions) is the assumed foundation for Year 12. It is not directly assessed by an internal assessment, but its content underpins Unit 3 and the External Assessment.
- Atomic structure, isotopes and relative atomic mass
- Electron configuration and periodic trends
- Ionic bonding and ionic lattices
- Covalent bonding, Lewis structures, VSEPR and polarity
- Metallic bonding and properties of metals
- Intermolecular forces and properties of covalent molecular substances
- The mole concept and stoichiometric calculations
- Enthalpy, exothermic and endothermic reactions, and calorimetry
Unit 2 (Year 11 foundation, not assessed by IA but examined in the EA)
Unit 2 (Molecular interactions and reactions) is the second half of the Year 11 sequence. It is not assessed by an internal assessment, but the gas laws, solution chemistry and introductory acid-base content appear in EA Paper 1 and underpin Unit 3 equilibrium and Unit 4 organic chemistry calculations.
Topic 1: Intermolecular forces and gases.
- Kinetic theory and the gas laws (Boyle, Charles, Gay-Lussac)
- The ideal gas equation and molar volume at SLC
- Stoichiometry of reactions involving gases
Topic 2: Aqueous solutions and acidity.
- Water as a solvent and the dissolution of ionic and polar substances
- Concentration and dilution of aqueous solutions
- Solubility rules and precipitation reactions (net ionic equations)
- The pH scale and introduction to acid-base chemistry
Unit 3, Topic 1: Chemical equilibrium systems
- Dynamic equilibrium in closed systems
- Le Chatelier's principle and equilibrium shifts
- The equilibrium constant Kc and reaction extent
- Bronsted-Lowry acids and bases
- pH, Kw and the self-ionisation of water
- Buffer systems and resistance to pH change
Unit 3, Topic 2: Oxidation and reduction
Unit 4, Topic 1: Properties and structure of organic materials
Unit 4 (Structure, synthesis and design) is the second half of Year 12. It feeds the IA3 research investigation (20 percent) directly and contributes roughly half of every EA paper.
- IUPAC nomenclature and functional groups
- Physical properties of organic compounds
- Structural and geometric isomerism
- Reactions of alkanes and alkenes
- Reactions of alcohols and esterification
- Reaction pathways and organic synthesis
Unit 4, Topic 2: Chemical synthesis and design
- Addition polymerisation and polymer properties
- Condensation polymers and biomolecules
- Green chemistry principles and atom economy
- Mass spectrometry and IR spectroscopy
- Proton (1H) NMR spectroscopy
- Chromatography techniques: TLC, GC and HPLC
How Unit 3 maps to the IAs
IA1 data test (10 percent). Expect Topic 1 stimulus most years: equilibrium concentration tables, ICE-style data, titration curves, Kc problems, pH calculations. Topic 2 sometimes appears as a reduction-potential table interpretation. Mark accuracy on units, significant figures, and explicit Le Chatelier reasoning.
IA2 student experiment (20 percent). The most common IA2 designs are: investigating the effect of concentration or temperature on equilibrium position (e.g. the iron(III) thiocyanate system); acid-base titration to determine the concentration of a household substance; or constructing a galvanic cell and comparing measured to theoretical cell potential. Strong reports identify a researchable question, justify the experimental design against Unit 3 theory, present clean processed data, evaluate uncertainty against the IA2 criteria, and extend the conclusion with a refined question.
EA Paper 1 and Paper 2. Around half the EA marks draw on Unit 3. Topic 1 questions cluster around Kc and Le Chatelier; Topic 2 questions cluster around cell potential calculations and constructed half-equations. The data-analysis style of IA1 reappears throughout Paper 2.
How Unit 4 maps to the IAs and EA
IA3 research investigation (20 percent). Unit 4 is the home of IA3. The investigation is a research-only secondary-data review, typically on an organic chemistry, polymer, biomolecule, green-chemistry, or spectroscopy claim. Strong reports identify a researchable question linked directly to a Unit 4 subject-matter dot point, evaluate the validity and reliability of the cited evidence, and conclude with a refined claim. The most common topic clusters are: green-chemistry evaluation of an industrial process (atom economy, energy use, renewable feedstocks); structure-property analysis of a polymer in a specified application; spectroscopic identification of an organic compound (MS, IR, NMR combined).
EA Paper 1 and Paper 2. Unit 4 contributes roughly half the EA marks. Paper 1 multiple choice routinely includes nomenclature, functional-group identification, isomerism, and IR / NMR interpretation. Paper 2 extended response usually contains at least one multi-step organic synthesis pathway and one spectroscopy-based identification.
How to use this hub
If you are starting Unit 3 this term: read the dynamic equilibrium and Le Chatelier dot points first. They underpin every Topic 1 question and most IA1 stimulus pieces.
If you are 2 weeks from IA1: focus on Kc, pH and the buffer dot point. Drill calculation accuracy under timed conditions. Practise interpreting unseen data tables.
If you are designing your IA2: read the dot point most relevant to your chosen experimental system, then read our QCE internal vs external assessments explainer for what QCAA's IA2 criteria reward.
If you are 6 weeks from the EA: revise the full Unit 3 set above, then complete Unit 4 revision. Past EA papers (released by QCAA after each year) are the best practice resource.
Calculators and ATAR planning
Our QCE ATAR calculator lets you enter your projected Chemistry result alongside your other General subjects to estimate your ATAR. Chemistry is a strong-scaling General subject in most years, so it disproportionately affects high-end aggregates.
The system around QCE Chemistry
QCE Chemistry sits inside the wider QCE system. Related explainers:
- How the QCE ATAR is calculated covers QTAC's top-5-General aggregate and scaling.
- Internal vs External Assessments breaks down the 50/50 IA/EA weighting for sciences.
- AARA special arrangements covers QCAA's Access Arrangements and Reasonable Adjustments.
- QCE exam day: what to actually expect covers EA logistics.
Every guide on this hub was written by ExamExplained (an initiative of Better Tuition Academy and XLev). For the official QCAA syllabus, IA syllabus specifications and past EA papers, refer to qcaa.qld.edu.au.
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Common questions about Chemistry
- QCE General Chemistry Year 12 (Units 3 and 4) is assessed across three internal assessments (IAs) and one External Assessment (EA). IA1 is a data test on Unit 3 stimulus (10 percent). IA2 is a student-designed experimental investigation (20 percent). IA3 is a research investigation (20 percent). The EA is a centrally-set 2-paper exam (50 percent). Unit 3 covers Equilibrium, acids and redox reactions; Unit 4 covers Structure, synthesis and design.
- Unit 3 is "Equilibrium, acids and redox reactions". Topic 1 covers chemical equilibrium systems (reversible reactions, dynamic equilibrium, the equilibrium law and Kc, Le Chatelier's principle), acids and bases (Bronsted-Lowry theory, pH, Kw, buffers), and applications to industrial equilibria. Topic 2 covers redox (oxidation numbers, half-equations, standard reduction potentials, galvanic cells, electrolysis). Unit 3 subject matter dominates IA1 and IA2.
- Chemistry sits in the top-5 General subjects aggregate for ATAR. QCAA does not pre-scale subjects; QTAC scales the cohort distribution at the end of the year. Chemistry has historically been one of the stronger-scaling General sciences in QLD because the cohort is academically rigorous (most students also take Specialist or Methods Mathematics).
- Chemistry is required for direct-entry medicine at UQ, JCU, Griffith and Bond, and for most biomedical, dentistry, pharmacy and veterinary pathways. Chemical and biomedical engineering require Chemistry; most other engineering degrees recommend it. Always check current QTAC prerequisite lists for your target courses.
- The EA is two papers, both sat in the assessment block at the end of Unit 4. Paper 1 is multiple choice and short response (60 marks). Paper 2 is extended response and data analysis (60 marks). Combined, the EA contributes 50 percent of the final subject result. The EA is cumulative across Units 3 and 4, so Unit 3 content remains examinable months after IA1 and IA2.
- IA1 is a 60 to 90-minute response to a previously unseen data set drawn from Unit 3 chemistry. You will see graphs, tables, equilibrium concentration values, titration curves, or reduction-potential data, and answer short and extended questions requiring claims, evidence and reasoning. Calculation accuracy and interpretive reasoning both matter. It is worth 10 percent of your subject result and usually sat in Term 1.
- Ionic: electrons are transferred between atoms (typically metal + non-metal); forms a lattice. Covalent: electrons are shared (non-metal + non-metal); forms discrete molecules or networks.
- pH = -log₁₀[H⁺]. For strong acids/bases, [H⁺] equals the concentration. For weak acids, use Ka. For buffers, use Henderson-Hasselbalch.
- When a system at equilibrium is disturbed (concentration, temperature, pressure change), the equilibrium shifts to partially counteract the disturbance.
- Identify the half-reactions (oxidation and reduction), balance atoms (excluding O and H), balance O with H₂O and H with H⁺, balance charge with electrons, then combine so electrons cancel.
- Enthalpy (ΔH) is the heat change of a reaction. Entropy (ΔS) is the change in disorder. Gibbs free energy (ΔG = ΔH - TΔS) tells you if the reaction is spontaneous.