CJC 2024 Prelim H1 Chem Paper 1 QP

1 CHEMISTRY 8873/01 Paper 1 Multiple Choice 12 September 2024 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, HT group and NRIC/FIN number on the Answer Sheet in the spaces provided. Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. 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. This document consists of 13 printed pages Catholic Junior College JC 2 Preliminary Examinations Higher 1

2 8873/01/CJC JC2 Preliminary Examination 2024 For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 A sample of bromine contains a mixture of two isotopes, 79Br and 81Br. The relative atomic mass of Br in this sample is 79.92. What is the percentage abundance of each isotope? 79Br 81Br A 46.0% 54.0% B 41.2% 58.8% C 54.0% 46.0% D 58.8% 41.2% 2 Use of Data Booklet is relevant to this question. How many atoms of silver (proton number 47) are there in a pure silver ring with a mass of 2.88 g? A 1.20 x 1021 C 1.20  1022 B 2.00 x 1021 D 1.61  1022 3 In an experiment, 100 cm3 of a 0.2 mol dm−3 solution of a metallic salt reacts exactly with 50 cm3 of 0.2 mol dm−3 aqueous sodium sulfite, Na2SO3. The half-equation for the oxidation of the sulfite ion is shown below: SO 2– 3 (aq) + H2O(l) → SO 2– 4 (aq) + 2H+(aq) + 2e− If the original oxidation number of the metal ion for the metallic salt is +3, what is the new oxidation number of the metal ion? A +1 B +2 C +4 D +5

3 8873/01/CJC JC2 Preliminary Examination 2024 [Turn over 4 A and B represent two consecutive elements in the periodic table. A2+ contains n protons while the cation of B contains (n+1) protons and is isoelectronic with A. What is the formula of the chloride formed by B? A BCl B BCl2 C BCl3 D BCl4 5 Which of the following is the correct electronic configuration of a c opper(II), Cu2+ ion in the ground state? A 1s2 2s2 2p6 3s2 3p6 3d9 4s2 B 1s2 2s2 2p6 3s2 3p6 3d10 4s1 C 1s2 2s2 2p6 3s2 3p6 3d10 D 1s2 2s2 2p6 3s2 3p6 3d9 6 Which of the following gives the symbols of elements in the order of decreasing first ionisation energy? A Cl, Br, I B F, Ne, Na C Al, Mg, Na D Cl, S, P 7 Which of the following have giant lattice structures under standard conditions at 298 K? 1 magnesium 2 buckminsterfullerene, C60 3 beryllium chloride 4 sodium fluoride A 1 and 2 only B 1 and 4 only C 3 and 4 only D 1, 2 and 4 only

4 8873/01/CJC JC2 Preliminary Examination 2024 8 Which of the following species has the smallest bond angle? A SO3 B BrF2+ C SF6 D IF2− 9 Which one of the following statements about aluminium chloride is incorrect? A AlCl3 has a simple molecular structure. B AlCl3 has a lower melting point than Al2O3. C The Al2Cl6 dimer contains intermolecular hydrogen bonding. D The reaction AlCl3 + Cl ‒ → AlCl4‒ involves the formation of a dative bond. 10 The table shows the boiling points of some halogenoalkanes. compound boiling point/ °C CH3Cl −24.2 CH3Br 3.6 CH3I 42.4 Which of the following correctly explains the difference in the boiling points? A the bond energy of C−X bond decreases from C−Cl to C−I. B the strength of permanent dipole-permanent dipole attractions increases from C−Cl to C−I. C the strength of instantaneous dipole-induced dipole attraction increases from CH3Cl to CH3I. D the electronegativity difference between the halogen and carbon increases from C−Cl to C−I. 11 Use of Data Booklet is relevant to this question. Which solid has the least exothermic lattice energy? A NaF B MgO C CaO D LiCl

5 8873/01/CJC JC2 Preliminary Examination 2024 [Turn over 12 Which equation correctly describes the standard enthalpy change of formation of water at 298K? A 2H(g) + 1 2O2(g) → H2O(g) B H2(g) + 1 2O2(g) → H2O(g) C H2(g) + 1 2O2(g) → H2O(l) D H+(aq) + OH−(aq) → H2O(l) 13 The gas-phase reaction of carbon monoxide with hydrogen forming methanol is as follows: 2H2(g) + CO(g) ⇌ CH3OH(g) The reaction was investigated by mixing 4.0 mol of H 2(g) with 2.0 mol of CO(g) in a 2.0 dm3 flask and allowing equilibrium to be established. At equilibrium, y mol dm-3 of H2 has reacted with CO(g). What is the equilibrium concentration of CO(g) in mol dm-3? A 1 - y B 1 - 𝑦 2 C 4 - 𝑦 2 D 4 - y 14 For a reversible reaction, what is the effect of a catalyst on the rate constant, kf for the forward reaction, the rate constant, kr, for the reverse reaction, and the equilibrium constant Kc? kf kr Kc A increase increase increase B no effect no effect increase C increase decrease no effect D increase increase no effect

6 8873/01/CJC JC2 Preliminary Examination 2024 15 When 10.00 cm3 of a 0.100 mol dm−3 NaOH is titrated against 0.100 mol dm−3 of aqueous CH3CO2H, the following titration curve is obtained. Which of the following points on the curve shows that it is functioning as a buffer? 1 Point W 2 Point X 3 Point Y 4 Point Z A 1 only B 1 and 2 only C 3 and 4 only D 4 only Volume of 0.100 mol dm−3 of CH3CO2H / cm3 pH 14 12 10 8 6 4 2 0 0 2 4 6 8 10 12 14 16 18 20 X Z W Y

7 8873/01/CJC JC2 Preliminary Examination 2024 [Turn over 16 Carbon-14 is an isotope of carbon. It is unstable and undergoes radioactive decay to form nitrogen-14. This radioactive decay is a first-order reaction with a half life of 5700 years. What is the molar proportion of carbon-14 to nitrogen-14 after a period of 17100 years? A 1:1 B 1:3 C 1:7 D 1:15 17 Hydrogen peroxide reacts with acidified iodide to form iodine. The following results were obtained. Expt No Initial concentration of reactants / mol dm−3 Initial rate of formation of iodine / mol dm−3 s−1 [H2O2] [I−] [H+] 1 0.010 0.010 0.10 2 x 10−6 2 0.010 0.010 0.20 2 x 10−6 3 0.020 0.010 0.10 4 x 10−6 4 0.020 0.030 0.10 1.2 x 10−5 Which of the following correctly explains the results? A The reaction is dependent on the concentration of the acid. B The reaction is overall first order. C The rate constant is 2.0 × 10−1 mol−1 dm3 s−1. D The rate equation for the reaction is rate = k[H2O2][I-].

8 8873/01/CJC JC2 Preliminary Examination 2024 18 Some data on two acid-base indicators are shown in the table below: indicator Approximate pH working range colour change acid alkali bromophenol blue 3.0 − 4.6 yellow violet bromothymol blue 6.0 − 7.6 yellow blue What conclusion can be drawn about a solution in which bromophenol blue is violet and bromothymol blue is yellow at 25 ºC? A It is weakly acidic. B It is strongly acidic. C It is neutral. D It is weakly basic. 19 Silicon is an element in the third period, Na to Ar, of the Periodic Table. Which statement is true for silicon? A The oxide of silicon reacts with water to give a basic solution. B Silicon has the highest melting point of the elements in this period. C Silicon is th