2025 A Level Chemistry B (Salters) H433/02 Scientific literacy in chemistry (Verified Question Paper With Mark Scheme Combined June 2025)

Monday 16 June 2025 – Morning A Level Chemistry B (Salters) H433/02 Scientific literacy in chemistry Time allowed: 2 hours 15 minutes (Verified Question Paper With Mark Scheme Combined June 2025) INSTRUCTIONS •Use black ink. You can use an HB pencil, but only for graphs and diagrams. •Write your answer to each question in the space provided. If you need extra space use the lined page at the end of this booklet. The question numbers must be clearly shown. •Answer all the questions. •Where appropriate, your answer should be supported with working. Marks might be given for using a correct method, even if your answer is wrong. INFORMATION •The total mark for this paper is 100. •The marks for each question are shown in brackets [ ]. •Quality of extended response will be assessed in questions marked with an asterisk (*). •This document has 20 pages. ADVICE •Read each question carefully before you start your answer. © OCR 2025 [601/5371/4] DC (PQ/CT) 344767/6 OCR is an exempt Charity Turn over 1This question is about reactions of haloalkanes. (a)CH3Cl is made by plants that grow on marshes. If CH3Cl reaches the stratosphere, electromagnetic radiation causes it to undergo homolytic fission forming chlorine radicals. (i)Give the systematic name of CH3Cl . . [1] (ii)Draw ‘half curly arrows’ to show the mechanism of the homolytic fission of CH3Cl . Show the products of the reaction. H H C Cl H [2] (iii)Which type of electromagnetic radiation causes this homolytic fission to occur in the stratosphere? . [1] (iv)The bond energy of the C–Cl bond is 346 kJ mol–1. Calculate the wavelength (in m) of radiation which breaks this bond. Give your answer to an appropriate number of significant figures. Wavelength = ..................................................... m [5] (v)Chlorine radicals catalyse the breakdown of ozone in the stratosphere. Write equations to show how this occurs and give the overall equation. Overall equation: [2] (vi)Why is the breakdown of ozone in the stratosphere harmful to humans? .......................................................................................................................................................... .......................................................................................................................................................... . [2] (b)CH3Cl reacts with ammonia to give an amine salt. CH3Cl + NH3 CH3NH3Cl Equation 1.1 Ammonia is acting as a nucleophile here. (i)Explain what is meant by the term nucleophile. .......................................................................................................................................................... . [1] (ii)Show the mechanism of Equation 1.1. Use curly arrows and show relevant lone pairs and the ionic products. H