OCR As Level Chemistry B Paper 1 2025 Mark Scheme

Get the official OCR AS Level Chemistry B (Salters) H033/01 Foundations of Chemistry mark scheme from the June 2025 examination series. This examiner-approved PDF contains the exact mark allocations, calculation methods, mechanism guidance, graph-analysis criteria, examiner annotations, level-of-response descriptors, and assessment-objective breakdowns used during live Summer 2025 OCR marking.

This mark scheme provides detailed examiner guidance for questions covering atom economy calculations, electrophilic aromatic substitution of bisphenol A derivatives, recrystallisation methods, free-radical substitution mechanisms, ozone depletion by chloroethane, intermolecular forces in haloalkanes, ideal gas equation calculations, combustion enthalpy calculations for cyclohexane, isotope peaks in mass spectrometry, electrolysis of sodium iodide, halogen displacement reactions, iodate(V) chemistry, oxidation-state analysis, and redox stoichiometry involving iodide and iodate ions. It includes accepted alternative answers, error-carried-forward guidance, significant-figure tolerances, graph-marking rules, practical-skills criteria, annotation conventions, and OCR examiner principles used in the live Summer 2025 series. Pair it with the matching OCR H033/01 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 Foundations of Chemistry, 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, combustion-enthalpy verification, electrolysis-answer checking, organic-mechanism assessment, graph-analysis practice, and identifying weaknesses in OCR AS Chemistry exam technique.