EJC Prelim H1 Chemistry Paper 2 Solutions

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2025 General Certificate of Education Advanced Level Higher 1 CANDIDATE NAME CIVICS GROUP 2 4 – INDEX NUMBER CHEMISTRY Paper 2 Structured Questions 8873/02 02 September 2025 2 hours Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not use paper clips, highlighters, glue or correction fluid. Write your name, civics group, registration number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Section A Answer all questions. Section B Answer one question. The number of marks is given in brackets [ ] at the end of each question or part question. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A 1 / 15 2 / 10 3 / 16 4 / 10 5 / 9 Section B 6 / 7 / 20 Total / 80 This document consists of 25 printed pages and 3 blank pages.

2 © EJC 8873/02/J2Prelims/25 For Examiner’s Use Section A Answer all questions in this section. 1 (a) Fig. 1.1 shows the trend for the third ionisation energies of a series of consecutive elements from the second and third period of the Periodic Table. Fig. 1.1 (i) Define the term third ionisation energy, with the aid of an equation for element A. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2] (ii) Explain the general trend in the 3rd ionisation energy from element C to I. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2] A B C D E F G H I 3rd ionisation energy element I Energy absorbed to remove 1 mole of electrons from 1 mole of doubly - charged, gaseous cation to form 1 mole of triply -charged, gaseous cation. A2+(g) → A3+(g) + e– 3rd IE generally increases from elements C to I. Nuclear charge increases. Shielding effect remains relatively constant due to same number of quantum shells. Effective nuclear charge increase s resulting in a stronger electrostatic attraction between valence electron and nucleus.

3 © EJC 8873/02/J2Prelims/25 [Turn over For Examiner’s Use (iii) Explain the decrease in the 3rd ionisation energy from element D to E. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [1] (iv) Deduce which group element C is found in. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2] (b) ⁵³X is an element produced by the decay of the radioactive isotope ⁵³Y. Complete Table 1.1. Table 1.1 species number of protons number of neutrons number of electrons electronic configuration 53 3 24 X + 1s2 ................................ .................. [2] (c) Catalytic converters are essential components in vehicle exhaust systems designed to reduce air pollution. It reduces harmful emissions from vehicle exhaust by using metals such as platinum, palladium, and rhodium as catalysts. (i) The metal catalysts in the catalytic converter are applied in the form of nanoparticles. Define the term nanoparticles. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [1] The electron is removed from the 2p subshell for E2+ is of higher energy than that of the electron in 2s subshell for D 2+. Hence, less energy is required to remove the valence 2p electron. Nanoparticles are discrete particles with all three dimensions in the size range between 1 to 100 nm. 24 29 21 2s2 2p6 3s2 3p6 3d3 The sharp drop in 3rd IE for C indicates that C 2+ has its valence electron removed from a principal quantum shell further from the nucleus , i.e. ns 1. Hence, C is in group 13.

4 © EJC 8873/02/J2Prelims/25 For Examiner’s Use (ii) Suggest how the catalytic converter, using the metals in nanoparticle form, is expected to reduce the cost of the converter while maximising its efficiency. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2] (iii) The harmful gases in the catalytic converters include carbon monoxide, nitrogen and unburnt hydrocarbons. State the type of catalysis and outline the mode of action as the metal catalysts convert the harmful gases into less harmful emissions. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [3] [Total: 15] Nanoparticles have high surface area to volume ratios so the higher surface energy allows for more effective collisions with reactant particles hence efficiency is not