Past-paper analysis
IB Chemistry HL past paper analysis
We tagged 248 questions worth 825 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. 77.7% of all marks sit in questions that join two or more topics.
- 248 questions
- 825 marks
- 15 papers
- New 2025 course
Written by Ejaz Ahmad. Published 18 October 2026. See how we analyse papers.
Marks by theme and topic
R3 · Mechanisms of change (24.6%) and S1 · Particulate matter (19.3%) take the largest shares of marks. S1.4 The mole / stoichiometry (9.9%), R3.2 Electron transfer: redox +HL (9.81%) and R3.1 Proton transfer: acids & bases +HL (8.78%) lead the table. The top five topics together carry 44.7% of all marks, and even the smallest of the 22 topics, S2.3 The metallic model, holds 1%.
Share of marks by theme
| Theme | % of all marks |
|---|---|
| R3 · Mechanisms of change | 24.6% |
| S1 · Particulate matter | 19.3% |
| R2 · How much / fast / far | 16.8% |
| S3 · Classification of matter | 14.6% |
| S2 · Bonding & structure | 13.3% |
| R1 · What drives reactions | 11.4% |
Share of all 825 marks.
Share of marks by topic
| Topic | % of all marks |
|---|---|
| S1.4 The mole / stoichiometry | 9.9% |
| R3.2 Electron transfer: redox +HL | 9.81% |
| R3.1 Proton transfer: acids & bases +HL | 8.78% |
| R2.2 Rate of chemical change +HL | 8.28% |
| S2.2 The covalent model +HL | 7.89% |
| S3.1 Periodic table & trends +HL | 7.83% |
| S3.2 Organic: functional groups | 6.8% |
| R2.3 Extent / equilibrium +HL | 4.56% |
| S1.3 Electron configurations | 4.31% |
| R1.2 Energy cycles +HL | 3.96% |
| R2.1 Amount of chemical change | 3.95% |
| R3.4 Electron-pair sharing (nucleophilic) +HL | 3.83% |
| R1.4 Entropy & spontaneity +HL | 3.62% |
| R1.1 Measuring enthalpy | 2.4% |
| S2.4 From models to materials | 2.3% |
| S1.1 Particulate nature of matter | 2.21% |
| R3.3 Electron sharing (radicals) | 2.13% |
| S2.1 The ionic model | 2.12% |
| S1.5 Ideal gases | 1.73% |
| R1.3 Energy from fuels | 1.4% |
| S1.2 The nuclear atom | 1.2% |
| S2.3 The metallic model | 1% |
Share of all 825 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 55% of the marks, Paper 1A (multiple choice) about 24% and Paper 1B (data / experimental) about 21%. 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 | 31.5 | 68.6 | 59.5 |
| S2 · Bonding & structure | 30 | 12.5 | 67.4 |
| S3 · Classification of matter | 34 | 18 | 68.7 |
| R1 · What drives reactions | 20.8 | 11.6 | 61.5 |
| R2 · How much / fast / far | 34.5 | 26.1 | 77.9 |
| R3 · Mechanisms of change | 49.1 | 38.2 | 115.2 |
Marks after multi-topic questions are split among their tags.
How hard the questions are
Most questions are mid-level: 132 of 248 sit in the medium band.
Questions by difficulty rating
| Rating | Questions | Share |
|---|---|---|
| Accessible | 80 | 32.3% |
| Medium | 132 | 53.2% |
| Hard | 36 | 14.5% |
Rated by our team when each of the 248 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 +HL, R3.1 Proton transfer: acids & bases +HL, R2.2 Rate of chemical change +HL and S2.2 The covalent model +HL). Together they carry 44.7% of marks.
- Expect mixed questions: 77.7% 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 1% 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 written for the redesigned course, first examined in 2025. 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.