RI 2019 Y5 Promo QP

RAFFLES INSTITUTION 2019 YEAR 5 PROMOTION EXAMINATION Higher 2 CHEMISTRY 9729 2 October 2019 2 hours 30 minutes Additional Materials: Multiple Choice Answer (OMR) Sheet Writing Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, index number and civics tutorial group in the spaces provided on the OMR Sheet, the cover sheets on pages 13 and 15, and the writing paper used for Section C. Do not use staples, paper clips, highlighters, glue or correction fluid. This paper consists of three sections, A, B and C. Section A (15 marks) Answer this section first. The OMR sheet will be collected after the first 30 minutes. There are fifteen questions in this section. 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. Read the instructions on the OMR 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 the question paper. Section B (35 marks) There are three questions in this section. Answers to this section are to be written in the spaces provided in the question paper. Section C (40 marks) There are three questions in this section. Answers to this section are to be written on the writing paper provided. You are to begin each question on a fresh sheet of paper. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten your answers to Section C securely together. Answers to Sections A, B and C are to be handed in separately. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 25 printed pages and 1 blank page.

2 © Raffles Institution 2019 9729/O/19 [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 Which statement is correct? A One mole of a compound is the amount that contains the same number of atoms as there are atoms in 12.000 g of carbon-12. B The relative molecular mass of a compound E is given by the following expression. average mass of one atom of E 1 12 the mass of one molecule of carbon-12 C The relative isotopic mass of lithium-7 is given by the following expression. average mass of all isotopes of lithium 1 12 the mass of one atom of carbon-12 D The relative atomic mass of oxygen is given by the following expression. average mass of one atom of oxygen 1 12 the mass of one atom of carbon-12 2 NaHCO3 (Mr = 84.0) undergoes decomposition to form Na2CO3, carbon dioxide and water vapour when heated. When 3.50 g of an impure sample of NaHCO3 was heated, the loss in mass was found to be 0.85 g. Assuming that the impurities do not decompose, calculate the percentage purity by mass of NaHCO3 in the sample. A 32.9% B 34.2% C 65.8% D 67.1%

3 © Raffles Institution 2019 9729/O/19 [Turn Over 3 Flerovium, F l, is produced by bombarding atoms of plutonium, Pu, with atoms of element X. The reaction that takes place is shown below. Pu94 244 + X ⎯→ Fl114 289 + 3 n0 1 Which row in the table correctly describes the nuclear makeup of X? number of protons number of neutrons A 20 28 B 20 48 C 23 42 D 23 20 4 Which statements are correct for the CO32– ion? 1 All the bond lengths are equal. 2 The hybridisation of the carbon atom is sp2. 3 The bond angle in CO32– is the same as that in SO32–. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 5 The reaction between ammonia, NH 3, and ethyne, C 2H2, to form butanenitrile, CH3CH2CH2CN, is hypothesised to be responsible for the red-orange hue of Jupiter’s Great Red Spot. NH3 + 2C2H2 ⎯→ CH2CH2CH2CN Which statements are correct? 1 Ethyne and butanenitrile have the same number of  bonds. 2 Ethyne forms stronger intermolecular forces of attraction than butanenitrile. 3 The C–H bond energy in ethyne is greater than that of C–Ha in butanenitrile. A 1 and 2 only C 2 and 3 only B 1 and 3 only D 2 only Ha

4 © Raffles Institution 2019 9729/O/19 [Turn Over 6 Two separate bulbs contain ideal gases A and B at 30 oC and 20 oC respectively. At these temperatures, the density of gas A is three times that of gas B. Given that the relative molecular mass of gas A is one quarter that of gas B, what is the value of pressure of gas A pressure of gas B ? A 0.776 C 12.4 B 1.13 D 18.0 7 The energy profile diagram for the conversion of E to F is shown below. Which statement is incorrect? A The overall enthalpy change of reaction is –30 kJ mol–1. B The activation energy for the first step is 100 kJ mol–1. C There is only one transition state in the reaction. D The first step is the rate-determining step. 8 The radii and charges of six ions are given below. ion J+ L+ M2+ X– Y– Z2– radius / nm 0.08 0.14 0.18 0.12 0.18 0.14 Which statements are correct? 1 JY has higher covalent character than LY. 2 The lattice energy of MZ is more exothermic than that of JX. 3 The hydration energy of J+ is less exothermic than that of L+. A 1, 2 and 3 C 2 and 3 only B 1 and 2 only D 1 only

5 © Raffles Institution 2019 9729/O/19 [Turn Over 9 The reaction between propanone, CH3COCH3, and iodine is catalysed by H+ ions. CH3COCH3 + I2 ⎯⎯⎯→ CH3COCH2I + HI The reaction is zero order with respect to iodine. A series of experiments was carried out using different volumes of aqueous solutions of propanone, iodine, hydrochloric acid and starch. Each reaction mixture was made up to the same total volume with water and the initial rate can be approximated as follows. initial rate  volume of aqueous I2 time taken for disappearance of deep blue colour The following results were obtained. reaction mixture volume of aqueous CH3COCH3 / cm3 volume of aqueous I2 / cm3 volume of aqueous HCl / cm3 volume of starch solution / cm3 volume of water / cm3 time taken for disappearance of deep blue colour / s 1 20 10 10 1 5 54 2 15 10 10 1 10 72 3 20 5 10 1 10 y 4 15 10 15 1 5 48 Which statements are correct? 1 y has a value of 27. 2 The order of reaction with respect to propanone is 1. 3 When HCl is replaced by H2SO4 of the same concentration, the time taken for the disappearance of deep blue colour remains unchanged. A 1 and 2 only C 2 and 3 only B 1 and 3 only D 2 only 10 The rate equation for the reaction 2P + Q2 + R ⎯→ P2Q + QR is given below. rate = k[P]2[Q2] What could be the mechanism for the reaction? A 2P + Q2 ⎯⎯⎯→ 2PQ PQ + R ⎯⎯⎯→ PQR PQ ⎯⎯⎯→ P + Q C P + Q2 ⎯⎯⎯→ PQ + Q PQ + P ⎯⎯⎯→ P2Q Q + R ⎯⎯⎯→ QR B Q2 + R ⎯⎯⎯→ QR + Q P + P ⎯⎯⎯→ P2 P2 + Q ⎯⎯⎯→ P2Q D P + P ⎯⎯⎯→ P2 P2 + Q2 ⎯⎯⎯→ P2Q + Q Q + R ⎯⎯⎯→ QR H+ slow slow slow slow

6 © Raffles Institution 2019 9729/O/19 [Turn Over 11 When water is added to the following equilibrium, the solution turns pink. CoCl42−(aq) + 6H2O(l) ⇌ Co(H2O)62+(aq) + 4Cl−(aq) blue pink Which statement best explains this observation? A Water catalyses the forward reaction, hence the rate of the forward reaction increases more than that o