OCR A Level Chemistry A (H432) Past Papers 2026

Periodic Table, Elements and Physical Chemistry

Duration: 2h 15m

Synthesis and Analytical Techniques

Duration: 2h 15m

Unified Chemistry

Duration: 1h 30m

Practical Activity Group

Duration: pass/fail

Kp and Kc equilibrium calculations — unit errors and wrong sign on square brackets

H432/01 in both 2023 and 2024 flags that candidates confuse Kp (partial pressures, no square brackets) with Kc (concentrations, square brackets), use incorrect units (e.g. atm–1 mol–1 instead of Pa), and make stoichiometry errors in RICE tables. RICE tables are explicitly recommended by examiners in both years.

H432/01

pH calculations — wrong method applied (weak-acid formula used for buffers)

H432/03 2024 Q1(c): squaring the H+ concentration for a buffer calculation was the most common error and earned no marks. Candidates need to identify the type of pH calculation (strong base, diluted strong acid, weak acid, or buffer) before selecting the method.

H432/01, H432/03

Transition metal definitions and electronic configurations — incorrect definition of d-block vs. transition element; wrong electron configurations for Cu2+ and Cr3+

H432/01 2023 LoR on d-block: only higher-attaining candidates scored full marks. Very few gave the correct definition of d-block element without substituting 'outermost' for 'highest energy'. Many omitted ions entirely from the transition element definition. Incorrect 4s2 configurations in ions were common.

H432/01

Optical isomerism — predicting the number of stereoisomers when multiple chiral centres are present

H432/02 2023 Q21(c)(i): very few candidates could apply the 2n formula. Most gave 4 (number of chiral centres) or 8 (2 × number of chiral centres) instead of 16 (2⁴) for four chiral centres.

H432/02

Organic synthesis route planning — wrong order of steps causing reagents to react with unintended functional groups

H432/02 LoR synthesis questions in both 2023 and 2024: many candidates identified the correct reagents but carried out steps in the wrong order. Common error in 2023: introducing CN– before HBr addition, causing both Br positions to react. Examiners cite knowing 'reagents for different functional group interconversions as well as planning each step' as the key discriminator.

H432/02

Group 2 and Group 7 ionic equations — wrong formulae, unbalanced equations, and spectator ion errors

H432/01 in both 2023 and 2024: ionic equations for Group 2 and Group 7 reactions were consistently poorly answered. Common errors: BaOH instead of Ba(OH)2; H2 instead of H2O as product; inclusion of spectator ions; unbalanced equations. Examiners recommend regular practice writing formulae and balancing equations.

H432/01

Reflux vs. distillation — not explaining the purpose of reflux in esterification and organic synthesis

H432/02 2024 Q23(a): only around a fifth of candidates correctly stated that reflux prevents loss of volatile compounds. Many gave generic or irrelevant explanations about bond breaking, reaction rate, or oxidation reactions. Candidates need to distinguish when reflux versus distillation is required.

H432/02

Novel synoptic contexts in H432/03 — applying inorganic knowledge in an organic-chemistry paper

H432/03 2024 Q5(b)(i): a large proportion of candidates suggested organic compounds when asked for chromium-containing species, revealing an assumption that H432/03 only requires organic responses. Examiners note that the synoptic paper requires inorganic and physical chemistry knowledge applied in any context.

H432/03