2025 H1 Chem 8873 Prelim P1 WORKED SOLUTIONS_CJC

1 CHEMISTRY 8873/01 Paper 1 Multiple Choice 18 September 2025 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, HT group and NRIC/FIN number on the Answer Sheet in the spaces provided. Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 10 printed pages Catholic Junior College JC 2 Preliminary Examinations Higher 1 WORKED SOLUTIONS

2 8873/01/CJC JC2 Preliminary Examinations 2025 For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 Use of the Data Booklet is relevant to this question. Which of the following contains 1 mole of the stated particle? A gold atoms in 79 g of solid gold B aqueous H+ ions in 10 dm3 of 0.10 mol dm-3 of H2SO4 solution C hydrogen atoms in 6 dm3 of methane gas at r.t.p. D chlorine molecules in 22.4 dm3 of chlorine gas at r.t.p. 2 Carbon disulphide vapour was burnt in oxygen according to the equation: CS2 (g) + 3O2 (g) → CO2 (g) + 2SO2 (g) A fixed amount of carbon disulphide was completely burnt in 100 cm3 of oxygen. Upon cooling, the mixture of gases was treated with an excess of aqueous sodium hydroxide and the volume of gas reduced by 30 cm3. All measurements were made at the same temperature and pressure. What was the final volume of gas left? A 10 cm3 B 30 cm3 C 40 cm3 D 70 cm3 Concept: Mole Concept and Stoichiometry Answer: C A Amount of Au atoms = mass/Mr = 79/197 = 0.401 mol B Amount of H+ ions = concentration × volume = 2 × 10 × 0.10 = 2.0 mol C At r.t.p., 1 mol of any gas occupies 24 dm3. Therefore, number of moles of gas in 6 dm3 = 0.25 mol In 1 mol of methane, there are 4 mol of H atoms. Amount of H atoms in 0.25 mol of methane = 4 × 0.25 = 1 mol D At r.t.p., 1 mol of any gas occupies 24 dm3. Therefore, number of moles of gas in 2.4dm3 = 22.4/24 = 0.933 mol

3 8873/01/CJC JC2 Preliminary Examinations 2025 [Turn over 3 Element X can exist in a few oxidation states. It was found that 0.01 mol of X2+ requires 0.004 mol of acidified potassium manganate (VII), KMnO4 for complete reaction. What is the final oxidation state of X in the above reaction? A +4 B +3 C 0 D −1 4 Use of the Data Booklet is relevant to this question. Which of the following has more