HCI Prelim P1 QP and Answers

This document consists of 14 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 17S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 9729/01 21 September 2018 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Complete the information on the Answer Sheet as shown below. There are 30 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 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.

© Hwa Chong Institution 2018 9729 / 01 / C2 Prelim 2018 2 1 The successive ionisation energies, in kJ mol–1, of an element X are given below. 870 1800 3000 3600 5800 7000 13200 What can be inferred from the data provided? A X has a half-filled p-subshell. B X has a giant covalent structure. C X is likely to form a compound with the formula BeX2 when reacted with beryllium. D X has a lower first ionisation energy than the element preceding it in the Periodic Table. 2 In which pair does the first species have a larger bond angle than the second? A CF 4 and BF3 B SO2 and CO2 C ClO3– and H2S D PO43– and NO3– 3 Silicon has a giant covalent structure similar to that of diamond. At room temperature, it is a very poor conductor. However, when heated to higher temperatures, its electrical conductivity increases. What is the best explanation for the increase in electrical conductivity at higher temperatures? A Heating ionises silicon to give Si 4+ ions. B Heating increases the frequency of vibration of silicon atoms. C Heating breaks some of the Si−Si bonds, allowing silicon particles to move. D Heating excites some of the valence electrons to higher energy levels such that they can be delocalised.

© Hwa Chong Institution 2018 9729 / 01 / C2 Prelim 2018 3 4 Measured values of the pressure, volume and temperature of a known mass of a gaseous compound are to be substituted into the ideal gas equation to calculate the relative molecular mass, Mr, of the compound. Which conditions of pressure and temperature would give the most accurate value of M r? pressure temperature A low low B low high C high high D high low 5 Which graph shows the behaviour of a fixed mass of an ideal gas at two constant temperatures, T1 and T2, where T2 > T1? A B C D T1 T2 p 1 / V 0 T2 T1 pV 1 / V 0 T2 T1 0 p V T1 and T2 V 0 pV T

© Hwa Chong Institution 2018 9729 / 01 / C2 Prelim 2018 4 6 When hydrogen chloride gas reacts with ammonia gas, ammonium chloride is produced which is seen as white fumes. Which statement about this reaction is incorrect? A Ammonia is a BrØnsted-Lowry base because it accepts a proton from hydrogen chloride. B Ammonia is a Lewis base because it donates its lone pair of electrons to a proton in hydrogen chloride. C Hydrogen chloride is an Arrhenius acid because it dissociates to give H + ion. D Hydrogen chloride is a Lewis acid because it accepts a lone pair of electrons from ammonia. 7 Aqueous chlorine is added to aqueous sodium iodide and the mixture was shaken with an equal volume of trichloromethane. Given that the density of trichloromethane is 1.48 g cm −3, which observation can be seen? A B C D 8 Use of the Data Booklet is relevant to this question. FeO 42– is a strong oxidising agent. It is produced by warming Fe(OH)3 with ClO– in alkaline medium. 2Fe(OH)3 + 3ClO– + 4OH– → 2FeO42– + 5H2O + 3Cl– The FeO 42– produced is typically precipitated out as BaFeO4 (Mr = 257.1) and it is kept in dark bottles for future usage. What can be deduced from the above information? 1 0.25 mol of Fe(OH) 3 and 0.40 mol of NaClO dissolved in excess NaOH solution can produce a maximum of 64.3 g of BaFeO4. 2 Eo(FeO42–/ Fe(OH)3) is likely to be less than +0.81 V. 3 BaFeO 4 is likely to be sensitive to light. A 1, 2 and 3 B 1 and 3 only C 2 and 3 only D 1 only colourless brown violet colourless colourless colourless colourless violet

© Hwa Chong Institution 2018 9729 / 01 / C2 Prelim 2018 5 9 When water freezes, 6.0 kJ mol−1 of heat enthalpy is evolved. What is the entropy change when 54 g of water freezes at 0 C? A –66 J K–1 B –22 J K–1 C 22 J K–1 D 66 J K–1 10 The initial rate of the slow reaction between peroxodisulfate( VI) and iodide ions can be studied by the "clock" method, using sodium thiosulfate. S 2O82– + 2I– → 2SO42– + I2 reaction I I2 + 2Na2S2O3 → 2NaI + Na2S4O6 reaction II When sodium thiosulfate is added to the reaction mixture, the iodine produced by reaction I will immediately react in reaction II until all the sodium thiosulfate has been used up. At that point, there will be a sudden appearance of a deep blue colour if starch is present. A series of experiments are carried out and the results are shown below. experiment volume of 0.200 mol dm –3 S2O82– /cm3 volume of 2.00 mol dm–3 I– /cm3 volume of 0.050 mol dm–3 Na2S2O3 /cm3 volume of starch solution /cm3 volume of water /cm3 time t /s Relative rate /s–1 1 10 20 2 4 14 56 0.0179 2 10 30 2 4 4 37 0.0270 3 10 10 1 2 2 28 0.0357 Which statements about the above reaction are correct? 1 The rate equation for this reaction is rate = k[S 2O82–][I–]. 2 The rate of formation of iodine in experiment 1 is 1.79 x 10 –5 mol dm–3 s–1. 3 Both Fe 2+ and Fe3+ can be catalysts for this reaction. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2 and 3

© Hwa Chong Institution 2018 9729 / 01 / C2 Prelim 2018 6 11 The numerical values of the equilibrium constant, Kp, for the reaction Ag2CO3(s) = Ag2O(s) + CO2 (g) are 3.20 × 10–3 and 1.50 at 298 K and 500 K respectively. Which statement is correct? A The backward reaction is endothermic. B The yield of carbon dioxide increases with temperature. C The value of Kp depends on the amount of Ag2CO3 used. D The yield of carbon dioxide will increase when Ag2O is removed. 12 At 500 K, an equilibrium exists for the dissociation of Al2Cl6. Al2Cl6(g) = 2AlCl3(g) A sample of Al 2Cl6 at a pressure of 0.72 atm was placed in an empty container and allowed to reach equilibrium at 500 K. The total pressure at equilibrium was 1.20 atm. Which statements are correct? 1 The degree of dissociation, α, is 0.67. 2 When volume of the container is halved, the position of equilibrium will shift to the left. 3 Both the rate constant and equilibrium constant would increase with temperature. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 13 Human plasma is buffered mainly by dissolved CO 2 which has reacted to form carbonic acid, H2CO3. H2CO3(aq) = H+(aq) + HCO3−(aq) Given that the pH of human plasma is 7.4 and the acid dissociation con