OCR As Level Chemistry B Paper 2 2025 Mark Scheme

Get the official OCR AS Level Chemistry B (Salters) H033/02 Chemistry in Depth mark scheme from the June 2025 examination series. This examiner-approved PDF contains the exact mark allocations, calculation methods, level-of-response descriptors, practical-marking guidance, examiner annotations, and assessment-objective criteria used during live Summer 2025 OCR marking.

This mark scheme provides detailed examiner guidance for questions covering catalytic converters and heterogeneous catalysis, energy profiles and Boltzmann distributions, hydration of ethene, sulfuric-acid addition mechanisms, cyclopentene carbocation formation, platinum-catalysed hydrogenation, E/Z stereoisomerism, Group 2 ionisation enthalpies and reactivity trends, preparation of hydrated magnesium sulfate crystals, sodium sulfite oxidation calculations using barium sulfate precipitation, hydrate graph analysis, isotope abundance calculations for magnesium, esterification reactions, equilibrium constants for esterification systems, titration calculations, and temperature effects on equilibrium position and Kc values. It includes accepted alternative answers, error-carried-forward guidance, graph-plotting tolerances, mechanism-arrow rules, significant-figure expectations, level-of-response criteria, and OCR annotation conventions used in the live 2025 series. Pair it with the matching OCR H033/02 June 2025 question paper on markscheme.net for complete examiner-style revision and exam preparation. Updated for the 2025/2026 academic year, mobile-friendly, and instantly downloadable from markscheme.net.

This document is designed for OCR AS Level Chemistry B (Salters) students preparing for the 2026 examination series, Year 12 learners studying Chemistry in Depth, retake students targeting A/A grades, and home-schooled candidates seeking examiner-level insight into OCR marking expectations.

It is also essential for teachers, private tutors, revision-course providers, and parents supporting Chemistry revision at home. The mark scheme can be used for mock-exam grading, equilibrium-calculation verification, graph-analysis assessment, mechanism checking, practical-skills evaluation, titration-answer validation, and identifying weaknesses in OCR AS Chemistry exam technique.