QCE Chemistry EA strategy: 2026 guide

How the EA is structured

QCAA Chemistry EA is two papers sat in the November assessment block.

Paper 1. 90 minutes plus 10 minutes perusal. 60 marks. Section A: approximately 20 multiple choice (1 mark each). Section B: approximately 40 marks of short response.

Paper 2. 90 minutes plus 10 minutes perusal. 60 marks. Section A: short and extended response. Section B: data analysis plus extended response.

Calculator-active. QCAA data booklet provided.

Cumulative across Unit 3 (energy and reactions) and Unit 4 (organic chemistry and analytical techniques).

Topic frequency analysis

Year on year, the following topics dominate the EA.

From Unit 3:

• Equilibrium and Kc calculations (every year).
• Le Chatelier predictions (every year).
• pH for strong and weak acids; buffer pH (every year).
• Titration curves and equivalence point (most years).
• Redox half-equations and standard reduction potentials (every year).
• Electrolysis with Faraday's law calculation (most years).
• Rate of reaction with activation energy (most years).
• Thermochemistry calorimetry calculation (most years).

From Unit 4:

• IUPAC naming of organic compounds (every year).
• Predicting reaction products from a named reaction class (every year).
• Multi-step synthesis pathway (most years).
• Integrated spectroscopy structural determination (most years).
• IR + NMR + MS combined interpretation (most years).

Calculation patterns

Equilibrium. ICE table. Substitute into Kc expression. Solve for unknown (often a quadratic; use the small-x approximation only when x is less than 5 percent of initial concentration).

pH (strong acid). $pH = -\log_{10}[H^+]$ where [H+] equals the acid concentration.

pH (weak acid). $K_a = \frac{[H^+][A^-]}{[HA]}$. Approximate $[H^+] = \sqrt{K_a c}$ when $c >> K_a$, otherwise solve the quadratic.

Buffer pH. Henderson-Hasselbalch: $pH = pK_a + \log_{10}([A^-]/[HA])$.

Titration. $c_1 V_1 / n_1 = c_2 V_2 / n_2$ for stoichiometric ratio $n_1 : n_2$.

Redox. Balance half-equations: balance atoms first (except H and O), then O with water, then H with H+, then charge with electrons. Combine half-equations matching electron count.

Faraday's law. $Q = It$. Moles deposited $= Q / (zF)$ where z is electrons per ion and F = 96500 C/mol.

Thermochemistry. $q = mc\Delta T$ for solution calorimetry. $\Delta H = -q / n$ (per mole of reaction).

Bond energy. $\Delta H = \sum E(\text{bonds broken}) - \sum E(\text{bonds formed})$.

Strategy by section

Multiple choice. Read the stem carefully. Eliminate two implausible options before deciding between the remaining two. Mark and move on if uncertain.

Short response. 2 to 4 marks. Identify the chemistry concept. Apply the formula. Show working. State the answer with units and sig fig.

Extended response (8 to 10 marks). Plan first (1 to 2 minutes). Identify the components. Structure the response with subheadings or clear paragraphs. Use chemical equations as part of the argument.

Worked example: extended response

"Outline a synthesis of ethyl ethanoate from ethanol as the only organic starting material. Justify the choice of conditions and predict possible side products."

Plan. Convert some ethanol to ethanoic acid (oxidation). Esterify the remaining ethanol with the ethanoic acid.

Step 1. Oxidation of ethanol to ethanoic acid using acidified potassium dichromate (orange to green colour change). Heat under reflux to prevent loss of volatile aldehyde intermediate; allow full oxidation to the acid.

Step 2. Esterification of ethanoic acid with remaining ethanol using concentrated H2SO4 catalyst.

Conditions. Excess ethanol shifts equilibrium toward product (Le Chatelier). Heat under reflux but distil ester off as it forms (driving equilibrium further toward product). Concentrated H2SO4 acts as both catalyst and dehydrating agent.

Side products. Incomplete oxidation gives ethanal. Dehydration of ethanol (with H2SO4) gives ethene. Distillation purifies.

Common student errors

Significant figures. 3 sig fig unless data specifies otherwise. pH to 2 decimal places.

Units missing. Every numerical answer needs units.

Markovnikov mistakes. In alkene plus HX, the H adds to the carbon with more hydrogens.

Wrong functional group identification in spectroscopy. Always check the data booklet ranges before assigning.

Catastrophic error compounding. If a result is implausible (negative concentration, pH above 14), recheck.

Calculator-style data interpretation. Always interpret numerically and chemically.

Six-week preparation routine

Weeks 1-2. Key knowledge review. QCAA Chemistry syllabus as checklist. Map each subject matter point to your notes. Identify gaps.

Weeks 3-4. Calculation drills. 30 minutes per day rotating through equilibrium, pH, redox, electrolysis, thermochemistry, organic naming. One past Paper 1 per week.

Week 5. Extended response and integrated spectroscopy. Practice 8 to 10 mark items. Build a personal cheat sheet of named reactions and their conditions. One past Paper 2 per week.

Week 6. Full timed exam pairs. Two Paper 1 plus Paper 2 pairs over the week, marked against QCAA reports. Identify topics with persistent errors and revisit.

QCAA marking criteria

The EA awards marks for:

1. Correct chemistry (right concept, right equation, right product).
2. Show working (method marks even if arithmetic slips).
3. Significant figures (3 sig fig unless specified).
4. Units throughout.
5. Clear scientific communication.

Top band requires consistency across all five.

In one sentence

QCE Chemistry EA rewards systematic calculation skill (equilibrium, pH, redox, electrolysis, thermochemistry), confident organic chemistry (naming plus reactions plus mechanism), integrated spectroscopy (IR plus NMR plus MS), and a six-week preparation routine that drills past papers under exam conditions.