RI 2023 Y5 Promotional Examination QP

Name: ( ) Class: 24S0______ R AFFLES INSTITUTION 2023 YEAR 5 PROMOTION EXAMINATION Hi gher 2 CHEMISTRY 9729 28 September 2023 2 hours 30 minutes Additional Materials: Multiple Choice Answer (OMR) Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, 6-digit exam index number and civics tutorial group in the spaces provided on the OMR sheet and the cover sheets on pages 1 and 19. Shade your 6-digit exam index number on the OMR sheet. This paper consists of three sections, A, B and C. S ection A (15 marks) consists of 15 multiple-choice questions. Answer this section first. The OMR sheet will be collected after the first 30 minutes. 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 OMR sheet. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in the question paper. Section B (35 marks) consists of 3 structured questions. Answer all questions in the spaces provided in the question paper. If additional space is required, you should use the page at the end of the booklet for Section B (page 18 ). The question number must be clearly shown. Section C (40 marks) consists of 3 free-response questions. Answer all questions in the spaces provided in the question paper. If additional space is required, you should use the pages at the end of the booklet for Section C (page s 31 – 32). The question number must be clearly shown. This document consists of 30 printed pages and 2 blank pages. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. The us e 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. For Examiner’s Use Only B1 / 10 B2 / 11 B3 / 14 This document is copyrighted, please do not reproduce it without permission

2 © Raffles Institution 2023 9729/S/23 [Turn Over Section A (15 marks) For each question, there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Methylamine, CH3NH2, is a colourless gas at room temperature. The following equation shows the complete combustion of CH3NH2. 4CH3NH2 + 9O2 → 4CO2 + 2N2 + 10H2O In an experiment, 20 cm 3 of CH3NH2 is mixed with 60 cm 3 of O2 at room temperature and pressure. The mixture is sparked, resulting in the complete combustion of CH 3NH2. The mixture is then cooled back to room temperature and pressure. What is the final volume of the mixture? A 30 cm3 C 90 cm3 B 45 cm3 D 95 cm3 2 Under alkaline conditions, manganate( VI) ions, MnO 42−, undergo disproportionation to form manganate(VII) ions, MnO4−, and one other manganese-containing product. 2 moles of MnO4− is formed when 3 moles of MnO42− undergoes disproportionation. What is the other manganese-containing product? A Mn(OH)2 C MnO2 B Mn(OH)3 D MnO43− 3 Tumbaga is a n alloy of copper and gold found in the pre -Columbian Mesoamerica civilisations. The information in the table was obtained by analysis of a sample of tumbaga. mass number 63 65 197 % abundance 62 32 6 Which Ar value for copper is given by these figures? A 59.9 C 63.7 B 63.5 D 71.7 This document is copyrighted, please do not reproduce it without permission

3 © Raffles Institution 2023 9729/S/23 [Turn Over 4 Use of the Data Booklet is relevant to this question. What do the ions 36S2− and 37Cl− have in common? 1 Both ions have the same nucleon number. 2 Both ions have an outer electronic configuration of 3s2 3p6. 3 Both ions have more electrons than neutrons. A 1 and 2 B 2 and 3 C 1 only D 2 only 5 The peroxide ion contains two oxygen atoms joined by a single covalent bond. In this question, × represents an electron from Ba and • represents an electron from O. Which dot-and-cross diagram shows the bonding present in barium peroxide? A C B D 6 Under which set of conditions is a gas least likely to show ideal gas behaviour? temperature / K pressure / Pa A 300 1.0 × 105 B 300 1.0 × 106 C 1000 1.0 × 105 D 1000 1.0 × 106 This document is copyrighted, please do not reproduce it without permission

4 © Raffles Institution 2023 9729/S/23 [Turn Over 7 Hot air balloons have openings to allow for air flow in and out of the balloons. The pressure in the balloon is therefore the same as that of the surrounding atmosphere. A partially inflated hot air balloon contains air with a volume of 5000 m3 at 25 oC and 1 atm. The air in the balloon is then heated to 65 oC, causing the balloon to expand to a volume of 5500 m3. What is the ratio of the number of moles of air in the heated balloon to the initial number of moles of air in the balloon? A 0.42 B 0.97 C 1.03 D 2.36 8 Phosgene, COCl2, decomposes to form carbon monoxide, CO, and chlorine, Cl2. COCl2(g) ⇌ CO(g) + Cl2(g) Kc = a Which expression, in terms of a, gives the equilibrium constant for the reaction below? 2CO(g) + 2Cl2(g) ⇌ 2COCl2(g) A 1 2a B – 2a C a2 D 1 a2 9 Methanoic acid, HCO 2H, is reacted with methanol, CH 3OH, which is contaminated with a small amount of ethanol, C2H5OH. The following equilibria are established. HCO 2H(l) + CH3OH(l) ⇌ HCO2CH3(l) + H2O(l) Kc = K1 HCO 2H(l) + C2H5OH(l) ⇌ HCO2C2H5(l) + H2O(l) Kc = K2 Which statements are correct? 1 The expression for K1 is [HCO2CH3][H2O] [HCO2H][CH3OH] . 2 K1 is much larger than K2 because there is much more CH 3OH present than C2H5OH. 3 Adding HCO2C2H5 to the equilibrium mixture will increase the amount of HCO2CH3. A 1, 2 and 3 B 1 and 3 only C 2 and 3 only D 1 only This document is copyrighted, please do not reproduce it without permission

5 © Raffles Institution 2023 9729/S/23 [Turn Over 10 The enthalpy changes of formation, ∆Hf, of both PCl3(l) and PCl5(l) are exothermic. PCl3 reacts with Cl2 as shown below. PCl3(l) + Cl2(g) → PCl5(l) ∆Hr = −124 kJ mol–1 Which pair of statements is correct? statement 1 statement 2 A ∆Hr is more negative than ∆Hf [PCl5(l)]. ∆Hf [Cl2(g)] is zero. B ∆Hr is more negative than ∆Hf [PCl5(l)]. ∆Hf [Cl2(g)] is positive. C ∆Hr is less negative than ∆Hf [PCl5(l)]. ∆Hf [Cl2(g)] is zero. D ∆Hr is less negative than ∆Hf [PCl5(l)]. ∆Hf [Cl2(g)] is negative. 11 Separate samples of 30 cm3 of 0.10 mol dm–3 NaOH(aq) were added to each of the different acid solutions. The initial temperature of each solution was 25 oC before mixing. Which statement describes the increase in temperature that occur s on mixing each of these three acids separately with NaOH? experiment acid concentration / mol dm–3 volume / cm3 1 H2SO4 0.10 20 2 HCl 0.10 20 3 CH3COOH 0.10 20 A The temperature rise in experiment 1 is 1.5 times of that in experiment 2. B The temperature rise in experiment 1 is 1.5 times of that in experiment 3. C The temperature rise in experiment 2 is 1.5 times of that in experiment 1. D The temperature rise in experiment 3 is 1.5 times of that in experiment 2. This document is copyrighted, please do not reproduce it without permission

6 © Raffles Institution 2023 9729/S/23 [Turn Over 12 Radioactive decay is a first-order reaction. The rate of decay of a radioactive isotope decreases from 200 counts per minute to 25 counts per minute after