Difficulty Verdict

The 2023 OCR AS Level Chemistry A (H032) papers represent a demanding assessment of the specification. While the multiple-choice section in H032/01 provided some accessible recall marks, the structured questions in both papers required a high level of mathematical precision and structural fluency. H032/02 in particular contained multi-step mathematical problems and experimental analysis questions that challenged even top-tier candidates.

Where the Marks Are Won or Lost

The core of this series was dominated by Enthalpy Changes (28 marks) and Amount of Substance (25 marks). In these physical chemistry sections, examiners set traps around unit conversions and experimental uncertainties. Many students lost marks on the 6-mark Level of Response question on the enthalpy of combustion of butan-1-ol by failing to calculate both the energy change \( q \) and the amount of substance \( n \) correctly, or by incorrectly using the mass of alcohol burnt in the \( q = mc\Delta T \) equation instead of the mass of the water.

Examiner Pitfalls

  • The Dilution Trap: In the Group 1 hydroxide titration calculation, a significant portion of candidates failed to scale up their calculated moles by a factor of 10 to account for the dilution from 25.0 cm³ to 250.0 cm³.
  • Vague Intermolecular Terminology: In explaining why \( MgS \) has a higher melting point than \( PCl_3 \), many candidates incorrectly suggested that covalent bonds are broken during the melting of \( PCl_3 \), failing to distinguish between weak London/dipole forces and strong electrostatic ionic bonds.
  • Radical Substitution Errors: In drawing propagation steps for 2-bromobutane, students frequently placed the radical dot on the wrong carbon atom (e.g., terminal instead of secondary position) or omitted the radical dots entirely on halogen intermediates.

Strategy & Preparation Tactics

To succeed in future series, students must master multi-step stoichiometric conversions and practice writing explicit explanations of structure and bonding. Do not rely on memorised definitions alone; you must be prepared to apply Cahn-Ingold-Prelog (CIP) priority rules to specific isomers and construct complete, balanced equations for non-standard organic transformations.