RI Prelim P1 (Qns)

© Raffles Institution 2020 9729/01/S/20 [Turn Over RAFFLES INSTITUTION 2020 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 24 September 2020 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, class and index number in the spaces provided on the Answer Sheet. 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 the question booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 15 printed pages.

© Raffles Institution 2020 9729/01/S/20 [Turn Over 2 1 A sample containing four isotopes of xenon has a relative atomic mass of 131. 31. The percentage abundances of the isotopes in the sample are shown below. What is the value of m? isotope mXe 131Xe 132Xe 134Xe percentage abundance 28.0 25.0 27.0 20.0 A 126 C 129 B 128 D 130 2 5 moles of halide ion, X −, can react with 1 mole of halate ion, XO n−, to form a single halogen-containing product. Which row shows the value of n and the identity of the halogen-containing product? n halogen-containing product A 1 X2 B 2 XO− C 3 X2 D 4 XO− 3 At 298 K, two vessels are connected by a stopcock. The 5 dm 3 vessel is filled with argon at a pressure of 150 kPa and the 10 dm3 vessel is filled with xenon at 350 kPa. The stopcock is then opened to allow the gases to mix at 298 K , resulting in a total pressure of P kPa. Subsequently, the two vessels are heated to a temperature of T K and the total pressure at T K is 600 kPa. Assuming that the gases do not react at all temperatures, what are the values of P and T? P T A 217 437 B 217 824 C 283 570 D 283 632

© Raffles Institution 2020 9729/01/S/20 [Turn Over 3 4 Use of the Data Booklet is relevant to this question. In a nuclear reaction, uranium-235 decays as shown below. 235U  96Rb + 135Cs + 4X What is X? A neutron C electron B proton D hydrogen-1 5 Oxides of elements Mg, Al, Si and P are separately added to water and the pH of their resultant mixtures are measured. Which graph shows the correct trends when the melting points of these elements are plotted against the pH of the resultant mixtures? A B C D

© Raffles Institution 2020 9729/01/S/20 [Turn Over 4 6 The graph below shows the solubility of a compound at different pH values. What could be the compound? A aluminium chloride C magnesium chloride B aluminium hydroxide D magnesium hydroxide 7 The graph shows the second ionisation energies of six consecutive elements with atomic numbers less than 20. Which statements are correct? 1 V could be helium. 2 W reacts more vigorously than X with water. 3 Y has a higher electrical conductivity than Z. A 1, 2 and 3 C 1 and 3 only B 1 and 2 only D 2 and 3 only

© Raffles Institution 2020 9729/01/S/20 [Turn Over 5 8 Which of the following increases down Group 2? A reducing power B electronegativity C magnitude of ∆Hhydration of the ions D magnitude of lattice energy of the chlorides 9 The structure of penta-1,3-diene is shown below. 1 2 3 4 5 Which statement about penta-1,3-diene is correct? A Both C1 and C3 are sp hybridised. B The C2–C3 bond is shorter than the C4–C5 bond. C There are four  bonds in a molecule of penta-1,3-diene. D The  electrons are able to move freely between C1 and C5. 10 In which of the following pairs does the first compound have a higher melting point than the second compound? first compound second compound A SiCl4 SiO2 B NaCl Na2O C NaCl AlCl3 D

© Raffles Institution 2020 9729/01/S/20 [Turn Over 6 11 Use of the Data Booklet is relevant to this question. A Born Haber cycle involving aluminium oxide is shown below. Which statement is correct? A The enthalpy change for step Q is +5137 kJ mol–1. B The sum of the first and second electron affinity of oxygen is +702 kJ mol−1. C The enthalpy change for step P is the sum of 2Hatom(Al) and 3 2 Hatom(O2). D Lattice energy of aluminium oxide is the sum of the enthalpy changes in steps P, Q, R and T. Al2O3(s) 2Al3+(g) + 3O2−(g) 2Al3+(g) + 3O(g) + 6e− 2Al(s) + 3 2 O2(g) 2Al(g) + 3O(g) energy / kJ mol–1 T P Q R S +2106 kJ mol−1 –1676 kJ mol−1 0

© Raffles Institution 2020 9729/01/S/20 [Turn Over 7 12 Consider the following reactions. reaction 1 2CO2(g) + 3H2O(g)  C2H6(g) + 7 2 O2(g) H = +1434 kJ mol−1 reaction 2 H2O(l)  H2O(g) H = y The standard enthalpy change of combustion of ethane is –1542 kJ mol−1. Which statements are correct? 1 y is +36 kJ mol−1. 2 At 373 K, S for reaction 2 is y 373 kJ mol−1 K−1. 3 Reaction 1 is spontaneous only at high temperatures. A 1 and 2 only C 2 and 3 only B 1 and 3 only D 2 only 13 Aircraft in the stratosphere releases nitrogen monoxide, NO, which catalyses ozone breakdown by the mechanism shown below. step 1: NO + O3  NO2 + O2 (slow) step 2: NO2 + O  NO + O2 (fast) Which statement regarding this catalysis mechanism is not correct? A NO2 is a free radical. B O is a reaction intermediate. C The reaction is overall second order. D NO acts as a homogeneous catalyst.

© Raffles Institution 2020 9729/01/S/20 [Turn Over 8 14 Manganate(VII) ions, MnO 4−, undergo a redox reaction in acidic solution with ethanedioate ions, C2O42−. 2MnO4− + 5C2O42− + 16H+  2Mn2+ + 10CO2 + 8H2O The reaction is very slow at room temperature and can be catalysed by Mn 2+ ions. Further studies show that in the presence of the Mn 2+ catalyst, the reaction follows a first-order kinetics with respect to the MnO4− ions. Which graphs are correct? 1 [MnO4−] time (no Mn2+ added) 2 rate time (no Mn2+ added) 3 rate [MnO4−] (with Mn2+ added) A 1, 2 and 3 C 1 and 3 only B 1 and 2 only D 3 only 15 Ammonia is manufactured industrially by the Haber Process. N2(g) + 3H2(g) ⇌ 2NH3(g) H < 0 The rate constants of the forward and backward reactions are given as k1 and k−1 respectively. What happens to k1, k−1 and the equilibrium position when temperature is increased? k1 k−1 equilibrium position A increases increases shifts right B increases decreases shifts right C increases increases shifts left D decreases increases shifts left 0 0 0

© Raffles Institution 2020 9729/01/S/20 [Turn Over 9 16 A sealed vessel of fixed volume contains a mixture of CO(g), H 2(g) and CH 3OH(l) at equilibrium. CO(g) + 2H2(g) ⇌ CH3OH(l) H < 0 At time t, the reaction mix ture is subjected to a change . The graph below shows the partial pressure of CO against time. Which changes, when carried out separately, could have given the graph above? 1 addition of H2(g) 2 removal of some CH3OH(l) 3 decrease in temperature A 1, 2 and 3 C 1 and 3 only B 1 and 2 only D 3 only