The Most-Tested Topics in IB Chemistry HL
Every IB Chemistry HL past-paper question, tagged to its syllabus topic — ranked by how often each is tested (2016–2025).
All topics (HL) ()
42 papers analysed · top 15 of 22 topics
| # | Topic | % of all HL questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Organic chemistry; functional groups; IUPAC naming; isomers; spectroscopy (HL) | 22.3% | 175 | 3.1 |
| 2 | Rate; collision theory; factors; catalysts; rate equations (HL); Arrhenius (HL) | 13.7% | 108 | 4.3 |
| 3 | Covalent bonds; VSEPR; polarity; intermolecular forces; hybridization (HL) | 13.2% | 104 | 4 |
| 4 | Periodic trends; groups; periods; transition elements (HL); oxidation states | 12.7% | 100 | 2.9 |
| 5 | Brønsted-Lowry; pH; strong/weak acids; neutralization; titration; buffers (HL) | 12.5% | 98 | 3.4 |
| 6 | Oxidation/reduction; half-equations; electrochemical cells; electrolysis; electrode potential (HL) | 11.8% | 93 | 2.9 |
| 7 | Mole; Avogadro's constant; molar mass; empirical/molecular formula; concentration | 11.3% | 89 | 4.9 |
| 8 | Balanced equations; mole ratios; limiting reactant; percentage yield; atom economy | 9.7% | 76 | 5.7 |
| 9 | Enthalpy; exothermic/endothermic; calorimetry; standard enthalpy | 8.1% | 64 | 2.9 |
| 10 | Emission spectra; energy levels; sublevels; orbitals; ionization energy (HL) | 7.8% | 61 | 4.1 |
| 11 | Dynamic equilibrium; Kc; Le Chatelier's principle; reaction quotient (HL) | 7% | 55 | 3.6 |
| 12 | Atomic structure; protons, neutrons, electrons; isotopes; mass spectra (HL) | 6.7% | 53 | 3.6 |
| 13 | Nucleophilic substitution; electrophilic addition; mechanisms (HL); benzene (HL) | 5.2% | 41 | 3 |
| 14 | Combustion; fossil fuels; biofuels; fuel cells; greenhouse effect | 5% | 39 | 5.9 |
| 15 | Bond enthalpy; Hess's law; Born-Haber cycle (HL) | 5% | 39 | 3.4 |
How this was measured
Based on OwlsPrep's database of IB Chemistry HL past papers (2016–2025), 786 questions each tagged to its syllabus topic. “% of all HL questions” = the share of all tagged IB Chemistry HL questions that test the topic. Because one question can test several topics, shares do not sum to 100%. HL papers include both core and AHL (HL-only) content. Figures are aggregate statistics from question metadata — no exam questions or mark schemes are reproduced.
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