OCR A Level Chemistry B Paper 1 2025 Mark Scheme

Get the official OCR A-Level Chemistry B (Salters) H433/01 Fundamentals of Chemistry mark scheme from the June 2025 examination series. This examiner-approved PDF contains the exact mark allocations, calculation methods, mechanism guidance, level-of-response descriptors, practical-marking criteria, examiner annotations, and assessment-objective breakdowns used during live Summer 2025 OCR marking.

This mark scheme provides detailed examiner guidance for questions covering greenhouse gases and infrared absorption, Tollens’ reagent oxidation chemistry, transition-metal electron configurations, catalytic converters, ozone depletion by chlorine radicals, gas-liquid chromatography, colorimetry, electrophilic addition mechanisms, heterogeneous catalysis and Boltzmann distributions, triglyceride formation and hydrogenation of oils, esterification and distillation techniques, dehydration of alcohols, aromatic-compound identification using IR and proton NMR spectroscopy, enthalpy changes of solution for ammonium nitrate, lattice enthalpy cycles, phosphate-buffer calculations, Arrhenius activation-energy calculations, bromate–iodide redox chemistry, and qualitative analysis of halide salts containing ammonium, copper(II), and iron(II) ions. It includes accepted alternative answers, error-carried-forward guidance, significant-figure rules, curly-arrow marking conventions, level-of-response criteria, annotation systems, and OCR examiner principles used in the live Summer 2025 series. Pair it with the matching OCR H433/01 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 A-Level Chemistry B (Salters) students preparing for the 2026 examination series, Year 13 learners studying Fundamentals 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, spectroscopy-answer verification, thermodynamics-calculation checking, equilibrium assessment, practical-skills evaluation, and identifying weaknesses in OCR Chemistry exam technique.