MI Prelim H1 Chem P2 QP for exchange

Class Adm No Candidate Name: This document consists of 22 printed pages and 2 blank pages. 2025 Preliminary Examination Pre-University 2 H1 CHEMISTRY 8873/02 Paper 2 Structured Questions 27 August 2025 2 hours Candidates answer on the Question paper. Additional materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not turn over this question paper until you are told to do so. Write your name, class and admission number in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. Question Section A Section B Total 1 2 3 4 5 / 6 Marks 19 11 22 8 20 80 H Class Adm. No.

2 Section A Answer all the questions in this section in the spaces provided. 1 (a) Graphene is a nanomaterial. (i) Draw a diagram to represent part of a graphene layer which contains at least five complete rings of carbon atoms. [1] (ii) Graphene has high tensile strength. Explain what this means. ...................................................................................................................................... ..................................................................................................................................[1] (iii) Explain why graphene has high tensile strength. ...................................................................................................................................... ..................................................................................................................................[1] (iv) Graphene is able to conduct electricity. Explain why. ...................................................................................................................................... ...................................................................................................................................... ..................................................................................................................................[1]

3 [Turn over (b) Nickel catalyses a reaction between methane and steam. (i) State the electronic configuration of Ni. 1s2 ............................................................................................................................[1] (ii) Outline the mode of action as nickel catalyses the reaction between methane and steam. Include bond forming and bond breaking in your answer. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ..................................................................................................................................[3] (iii) The nickel catalyst is made of nanoparticles. Explain what it means by a nanoparticle. ...................................................................................................................................... ..................................................................................................................................[1] (iv) Explain how nickel being made of nanoparticles would facilitate the catalysis of the reaction. ...................................................................................................................................... ..................................................................................................................................[1]

4 (c) Methane and steam react to form a mixture of carbon monoxide and hydrogen known as syngas. All four gases exist as an equilibrium mixture. CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) ΔH (i) In the carbon monoxide molecule, one of the covalent bonds is a dative bond. Draw the ‘dot -and-cross’ diagram to show the bonding in a molecule of carbon monoxide. [1] (ii) Use bond energy values from the Data Booklet to calculate the enthalpy change of the forward reaction, ΔH. [2] (iii) In the manufacture of syngas, 1.00 mol of CH4(g) and 1.00 mol of H2O(g) were injected into a 2.00 dm3 reaction chamber at 700 °C. At equilibrium, 0.26 mol of CO(g) was formed. Calculate the equilibrium constant, Kc, for the reaction at 700 °C. [2]

5 [Turn over (iv) With reference to your answer in (c)(ii), explain how increasing the temperature to 1000 °C would affect the equilibrium position and Kc value. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ..................................................................................................................................[2] (v) At time t1, the reaction chamber was suddenly compressed such that its volume decreased. Complete the graph below until time t2 to show how the concentrations of CO(g) and H2(g) would change as a result of the sudden compression. [2] [Total: 19] concentration time 0 t1 H2(g) CO(g) t2

6 2 (a) Hydrogen halides are molecules consisting of a hydrogen atom covalently bonded to a halogen atom. HF HCl HBr HI boiling point / °C 20 –85 –66 –35 (i) Explain the relative boiling points of the 4 hydrogen halides shown above. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ..................................................................................................................................[3] (ii) State and explain the trend in thermal stability of the 4 hydrogen halides shown above. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ....................................................................................