JPJC 2025 H2 Chemistry Promos P2

© Jurong Pioneer Junior College [Turn Over NAME CLASS 25S JURONG PIONEER JUNIOR COLLEGE JC1 YEAR END EXAMINATION 2025 CHEMISTRY 9476/02 Higher 2 Paper 2 Structured Questions 2 October 2025 2 hours Candidates answer on the Question paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a HB pencil for any diagrams, graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 9 2 8 3 11 4 13 5 9 Section B 6 20 Penalty (delete accordingly) Lack 3sf in final answer –1 / NA Missing/wrong units in final ans –1 / NA Bond linkages –1 / NA Total 70 This document consists of 23 printed pages inclusive of 2 blank pages.

2 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over Section A (50 marks) Answer ALL the questions in the spaces provided. 1 (a) Complete Fig. 1.1 below to show: • the labelling of all the orbitals • the arrangement of electrons in the orbitals of Al atom. The labelling for 1s orbital and the 1s electrons of Al are shown below. For Examiner’s Use [2] Energy Nucleus 1s Fig. 1.1

3 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over (b) The ionic radii of the Period 3 elements are shown in Fig. 1.2 below. Fig. 1.2 For Examiner’s Use (i) Explain why the ionic radius decreases from Na+ to Mg2+ to Al3+. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (ii) Suggest why the ionic radii of the anions P3–, S2– and Cl– are larger than that of the cations Na+, Mg2+ and Al3+. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] Na+ Mg2+ Al3+ P3− S2− Cl−

4 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over (c) The detection of 27Al3+ ions is crucial as they are harmful and associated with Alzheimer's disease. In an experimental set-up to detect 27Al3+ ions, beams of charged ions are deflected by an electric field. It was observed experimentally that a beam of 16O2– was deflected by an angle of 27.8o. Calculate the value of the angle of deflection of a sample of 27Al3+. For Examiner’s Use ……………………….………………………………………………………………… ………………………………………………………………………………………… ……………………….………………………………………………………………… ………………………………………………………………………………………… ……………………….………………………………………………………………… ………………………………………………………………………………………… ……………………….………………………………………………………………… ………………………………………………………………………………………… ……………………….………………………………………………………………… [1] (d) (i) Draw the dot -and-cross diagram showing the electrons (outer shells only) for the AlCl4− ion. By considering the electron pairs around the central atom, predict the Cl-Al-Cl bond angle in the AlCl4− ion. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (ii) At certain temperatures, aluminium chloride exists as Al2Cl6 molecules. Draw the structure of Al2Cl6. Label the co -ordinate (dative) bonds on your structure. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] [Total:9]

5 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over Blank Page

6 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over 2 (a) Dolomite is a carbonate-containing mineral with the formula MgE(CO3)2 where E is a metal ion. MgE(CO3)2 is insoluble in water but dissolves in acid. The reaction between hydrogen ions and carbonate ions is shown below. reaction (1) 2H+ + CO32− → CO2 + H2O A 4.99 g sample of dolomite , MgE(CO3)2, was added to 50.0 cm 3 of 3.00 mol dm-3 hydrochloric acid, HCl, which is in excess. After effervescence of CO2 has stopped, the resulting solution is made up to 250 cm3 in a volumetric flask, using deionised water and labelled as solution F. 25.0 cm3 of solution F required 21.00 cm3 of 0.198 mol dm-3 sodium hydroxide, NaOH for complete reaction. For Examiner’s Use (i) Calculate the amount of HCl acid in 250 cm3 of solution F. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] (ii) Calculate the amount, in moles, of HCl acid that reacted with the sample of dolomite, MgE(CO3)2, in reaction (1). ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] (iii) Calculate the amount of carbonate ions , CO32−, in the sample of dolomite, MgE(CO3)2. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1]

7 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over (iv) Determine the relative atomic mass of E. For Examiner’s Use ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… …………………………………………………………………………………. ………………………………………………………………………………… [2] (b) 100 cm 3 of 0.438 mol dm -3 of aqueous barium hydroxide, Ba(OH) 2, a strong base, was added to 100 cm 3 of 1.20 mol dm -3 aqueous HCl acid and the temperature of the mixture rose by 6 oC. Assume that the specific heat capacity of all solutions are 4.18 J cm–3 K–1. (i) Calculate the enthalpy change of neutralisation for this reaction. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (ii) Explain why the enthalpy change of neutralisation would be less exothermic if ethanoic acid, CH3CO2H is used instead of HCl acid. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] [Total:8]

8 © Jurong Pioneer Junior College 9476/02/EOY/2025 [Turn Over 3 (a) Nitrate ions