OCR A Level Chemistry B Paper 2 2025 Mark Scheme

Get the official OCR A-Level Chemistry B (Salters) H433/02 Scientific Literacy in Chemistry mark scheme from the June 2025 examination series. This examiner-approved PDF contains the exact mark allocations, calculation methods, indicative scientific points, level-of-response descriptors, graph guidance, examiner annotations, and assessment-objective breakdowns used during live Summer 2025 OCR marking.

This mark scheme provides detailed examiner guidance for questions covering homolytic fission of chloromethane, ultraviolet absorption and ozone depletion, nucleophilic substitution with ammonia, haloalkane reactivity trends, nitrogen chemistry in soils, ammonium-ion oxidation, nitrous oxide gas-volume calculations, molecular shapes and bond angles in nitrate ions and ammonia, kinetics of nitrogen monoxide reactions with chlorine, rate equations, second-order reactions, rate-determining steps, vancomycin molecular recognition, hydrogen bonding in peptides, pharmacophores, instantaneous dipole–induced dipole forces, lithium-ion versus vanadium redox-flow batteries, vanadium oxidation states, electrode potentials, redox equations, and transition-metal colour explanations. It includes accepted alternative answers, graph-plotting tolerances, error-carried-forward guidance, significant-figure rules, level-of-response criteria, annotation conventions, and OCR examiner principles used in the live 2025 series. Pair it with the matching OCR H433/02 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 A-Level Chemistry B (Salters) students preparing for the 2026 examination series, Year 13 learners studying Scientific Literacy in 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, kinetics-answer verification, electrochemistry assessment, graph-analysis training, organic-mechanism checking, and identifying weaknesses in OCR Chemistry exam technique.