Past-paper analysis
IB Chemistry SL past paper analysis
We tagged 191 questions worth 525 marks from 15 papers of the redesigned course, first examined in 2025. This page shows what each theme and topic is worth and which paper carries the marks. 69.3% of all marks sit in questions that join two or more topics.
- 191 questions
- 525 marks
- 15 papers
- New 2025 course
Written by Ejaz Ahmad. Published 18 October 2026. See how we analyse papers.
Marks by theme and topic
S1 · Particulate matter (25.9%) and R3 · Mechanisms of change (25%) take the largest shares of marks. S1.4 The mole & stoichiometry (13.94%), R3.2 Electron transfer (redox) (11.02%) and S2.2 The covalent model (8.86%) lead the table. The top five topics together carry 50% of all marks, and even the smallest of the 21 topics, S2.3 The metallic model, holds 0.88%.
Share of marks by theme
| Theme | % of all marks |
|---|---|
| S1 · Particulate matter | 25.9% |
| R3 · Mechanisms of change | 25% |
| R2 · How much / fast / far | 18% |
| S2 · Bonding & structure | 14% |
| S3 · Classification of matter | 8.7% |
| R1 · What drives reactions | 8.5% |
Share of all 525 marks.
Share of marks by topic
| Topic | % of all marks |
|---|---|
| S1.4 The mole & stoichiometry | 13.94% |
| R3.2 Electron transfer (redox) | 11.02% |
| S2.2 The covalent model | 8.86% |
| R2.2 Rate of chemical change | 8.21% |
| R3.1 Proton transfer (acids & bases) | 8.01% |
| R2.3 Extent / equilibrium | 5.39% |
| S1.3 Electron configurations | 5.01% |
| S3.2 Functional groups (organic) | 4.49% |
| R2.1 Amount of chemical change | 4.42% |
| S3.1 Periodic table & trends | 4.17% |
| R1.1 Measuring enthalpy | 3.7% |
| R3.3 Electron sharing (radicals) | 3.29% |
| R1.2 Energy cycles | 3.16% |
| S1.1 Particulate nature of matter | 2.78% |
| R3.4 Electron-pair sharing (nucleophilic) | 2.67% |
| S1.5 Ideal gases | 2.52% |
| S2.1 The ionic model | 2.18% |
| S2.4 From models to materials | 2.04% |
| R1.3 Energy from fuels | 1.67% |
| S1.2 The nuclear atom | 1.6% |
| S2.3 The metallic model | 0.88% |
Share of all 525 marks. Marks from multi-topic questions are split equally between their tags.
Paper 1A, Paper 1B and Paper 2
Marks attributed to each theme on each paper. Paper 2 (extended response) carries about 48% of the marks, Paper 1A (multiple choice) about 29% and Paper 1B (data / experimental) about 24%. Paper 1A is multiple choice, Paper 1B is data-based and experimental, Paper 2 is extended response.
Marks attributed to each theme, by paper
| Theme | Paper 1A (multiple choice) | Paper 1B (data / experimental) | Paper 2 (extended response) |
|---|---|---|---|
| S1 · Particulate matter | 32.2 | 53.8 | 49.8 |
| S2 · Bonding & structure | 26 | 9 | 38.2 |
| S3 · Classification | 20.5 | 2.5 | 22.5 |
| R1 · What drives reactions | 10.8 | 10.3 | 23.5 |
| R2 · How much / fast / far | 26.8 | 17.5 | 50.3 |
| R3 · Mechanisms of change | 33.6 | 31.8 | 65.7 |
Marks after multi-topic questions are split among their tags.
How hard the questions are
Most questions are mid-level: 102 of 191 sit in the medium band.
Questions by difficulty rating
| Rating | Questions | Share |
|---|---|---|
| Accessible | 68 | 35.6% |
| Medium | 102 | 53.4% |
| Hard | 21 | 11% |
Rated by our team when each of the 191 questions was tagged.
What this means for your revision
- Start with the top five topics (S1.4 The mole & stoichiometry, R3.2 Electron transfer (redox), S2.2 The covalent model, R2.2 Rate of chemical change and R3.1 Proton transfer (acids & bases)). Together they carry 50% of marks.
- Expect mixed questions: 69.3% of marks sit in questions tagged with two or more topics. Practise linking topics, not only revising them one at a time.
- Bank the shorter marks on Paper 1A (multiple choice) and Paper 1B (data / experimental), then spend your long-answer time on Paper 2 (extended response), where most marks sit.
- Do not drop the small topics. The smallest, S2.3 The metallic model, still holds 0.88% of marks.
Past frequency shows where marks have gone so far. It does not promise what a future paper will contain.
All courses
IB past paper analysis
The same analysis for every Maths, Physics, Chemistry and Biology course.
Method
We counted the 15 papers from the two real sittings of the new course so far, May 2025 and November 2025. No specimen paper is included. Papers from the old course are left out because its topics and paper structure were different. Each question is read and tagged by topic. When a question carries more than one tag, its marks are split equally between them, so nothing is counted twice and the shares add up to 100%.
Tagging involves judgement, and these are counts of past marks, not a forecast. Read the full method.