AQA A-Level Chemistry revision: the papers, the MCQ, the plan
AQA A-Level Chemistry (7405) is three two-hour papers. Paper 1 (105 marks) is physical plus inorganic, Paper 2 (105 marks) is physical plus organic, and Paper 3 (90 marks) covers everything including 30 marks of multiple choice. Physical chemistry recurs on all three papers, so it carries the most weight. Revision should drill physical calculations as a skill, learn mechanisms for Paper 2, and practise the fast multiple-choice section that ends Paper 3.
AQA chemistry splits cleanly: inorganic on Paper 1, organic on Paper 2, and then Paper 3 tests whether you can do both plus the practical skills. The detail nobody warns you about is that physical chemistry is on all three — it is the strand that decides your grade, because it is the strand that is everywhere.
The specification, in plain English
| Paper | Content | Time | Marks | Weight |
|---|---|---|---|---|
| Paper 1 | Physical + inorganic (with practical skills) | 2 hours | 105 | 35% |
| Paper 2 | Physical + organic (with practical skills) | 2 hours | 105 | 35% |
| Paper 3 | All content + practical skills + 30 MCQ | 2 hours | 90 | 30% |
Physical chemistry — atomic structure, bonding, energetics, kinetics, equilibria, thermodynamics, acids and bases — appears on all three papers, which makes it the single highest-value revision strand. Paper 3's last section is 30 marks of multiple choice covering the whole spec: designed to be done fast, and designed so that the wrong options are the common errors.
What AQA asks that trips people up
- The multiple-choice section — a mark a minute or faster, and the distractors are your predictable errors.
- 'Explain' questions on trends — the answer is always a named concept (shielding, nuclear charge, energy levels), not a description of the trend.
- Practical questions on the twelve required practicals — method, variables, errors, treated as examinable content.
- Synthesis questions on Paper 2 — multi-step routes where each step is a mark.
- Signs and units in physical chemistry — ΔH, electrode potentials, and the calculations where they go wrong.
Worked questions in the AQA style
Calculate the pH of a buffer made from 0.10 mol dm⁻³ ethanoic acid (Ka = 1.7 × 10⁻⁵) and 0.15 mol dm⁻³ sodium ethanoate.
- Buffer formula: [H⁺] = Ka × [acid]/[salt].
- Substitute: [H⁺] = 1.7 × 10⁻⁵ × (0.10/0.15) = 1.13 × 10⁻⁵.
- pH = −log(1.13 × 10⁻⁵) ≈ 4.95.
- Check the direction — more salt than acid should push pH slightly above pKa (4.77). It does. A sanity check catches most buffer errors.
pH ≈ 4.95. The ratio is the whole question — get acid/salt the right way up.
Which row gives the correct shape and bond angle for BF₃? A) trigonal planar, 120° B) pyramidal, 107° C) tetrahedral, 109.5° D) bent, 104.5°
- BF₃ has three bonding pairs and no lone pairs on boron.
- Three pairs, no lone pairs → trigonal planar, 120°.
- The distractors are the other VSEPR shapes — the speed test is pairing electron-pair count to shape instantly.
- Option A. These questions are won on recall speed, not reasoning.
A) trigonal planar, 120°. The MCQ section rewards instant VSEPR recall.
Common AQA mistakes
- Spending three minutes on a one-mark MCQ — flag it, bank the rest, return.
- Buffer and Kc calculations with the ratio upside down — write the expression before substituting.
- Mechanisms with arrows from charges instead of lone pairs.
- Trend explanations that describe rather than explain — name the concept.
- Practical questions answered vaguely — AQA wants the controlled method, the named variable, the specific error.
Your AQA checklist
- I can do a full MCQ section in under thirty minutes.
- My physical chemistry calculations (Kc, pH, buffers, electrode potentials) are fluent.
- I can draw every mechanism type with correct curly arrows.
- I can describe each of the twelve required practicals as method, variables, errors.
- I can plan a two- or three-step synthesis between given compounds.
- I have done timed papers per paper code and checked explanations against the mark scheme.
When a mechanism keeps being wrong in the same place — the arrow direction, the intermediate, the conditions — it is usually one specific misunderstanding, not a general weakness. Show it to Lumi and it will draw the mechanism with you, arrow by arrow, until the rule behind it is visible.
What to take from this
- Physical chemistry is on every paper — it is the highest-value revision territory.
- Paper 3 ends with 30 marks of multiple choice — fast, fiddly, and designed to catch hesitation.
- Mechanisms are drawn, not described — curly arrows from lone pairs, not charges.
- Twelve required practicals are examined as method and analysis questions.
- AQA mark schemes want the named concept — 'shielding', 'nuclear charge', 'activation energy'.
Questions people also ask
Thirty marks' worth — usually 30 one-mark questions at the end of the paper covering the whole spec. They are designed to be quick; the skill is instant recall, not working.
Paper 2 (organic) for most students — the synthesis and mechanism questions carry the hardest marks. Paper 3 is broader but shallower; Paper 1 is the most predictable.
Yes — as questions on method, variables, errors and analysis across all three papers, and AQA says at least 15% of marks relate to practical work. The endorsement is separate pass/fail.
At least 20% of marks: logarithms for pH, rearranging for Kc and rate equations, standard form, and graph skills for kinetics. It is the most mathematical A-Level science.