2024 ACJC Prelim H1 Chem Paper 1 (Solutions)_

This document consists of 13 printed pages and 1 blank page. Anglo-Chinese Junior College JC2 Preliminary Examination Higher 1 CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 8873/01 9 September 2024 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, Centre number and index number on the Answer Sheet in the spaces provided unless this has been done for you. 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.

2 © ACJC 2024 8873/01/Preliminary Examination/2024 [Turn over ACJC H1 Chem Prelim 2024 Paper 1 Answers 1 C 11 D 21 C 2 B 12 B 22 A 3 C 13 C 23 B 4 B 14 A 24 C 5 B 15 A 25 A 6 D 16 B 26 D 7 C 17 C 27 C 8 A 18 A 28 B 9 D 19 D 29 B 10 B 20 A 30 D 1 Carbon sulfide, CS2, is a volatile flammable liquid used in the manufacture of cellophane. On combustion, CS2 is oxidised as follows. CS2(g) + 3O2(g) → CO2(g) + 2SO2(g) A 20 cm3 sample of carbon disulfide vapour is ignited with 100 cm 3 of oxygen. The final volume of gas after burning is treated with an excess of aqueous alkali. What percentage of this final volume dissolves in the alkali? [all volumes measured at the same temperature and pressure.] A 20% B 40% C 60% D 80% Answer: C Thinking process only acid will react & dissolve in alkali. From the above equation, CO2 & SO2 are both acidic gases [learn in periodicity] since the reactants & products are all gases, we can assume volume ratio as mole ratio. CS2(g) ≡ CO2(g) ≡ 2SO2(g) 20 : 20 : 2(20) So the reaction produces 20 + 40 = 60 cm3 of acidic gases.

3 © ACJC 2024 8873/01/Preliminary Examination/2024 [Turn over Volume of O2 required to burn 20cm3 of CS2 = 20 x 3 = 60cm3 Volume of O2 unreacted = 100 – 60 = 40cm3 Total volume of gas at the end of reaction = (acidic gases CO2 + SO2 + unreacted O2) = 60 + 40 = 100 cm3 % of final vol that dissolve in alkali = 60/ 100 x 100 % = 60 % 2 2 moles of nitric acid, HNO3, a powerful oxidising agent, reacts with 3 moles of hydrogen sulfide