2025 RI H1Chem Prelims P1 Questions

RAFFLES INSTITUTION 2025 YEAR 6 PRELIMINARY EXAMINATION Higher 1 CHEMISTRY 8873 / 01 Paper 1 Multiple Choice 26 September 2025 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, highlighters, glue or correction fluid. Write your name, class and index number in the spaces provided on the Answer Sheet. There are thirty questions in this section. 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 12 printed pages.

2 © Raffles Institution 2025 8873/01/S/25 [Turn Over 1 Which statement about 32S2− and 34S is correct? A Both have the same number of protons. B Both have the same number of electrons. C Both have the same number of neutrons. D Both have the same mass number. 2 Which statement about orbitals and electrons in an argon atom is correct? 1 The shell with principal quantum number 3 has no unpaired electrons. 2 The valence electronic configuration of an isolated atom is 3s2 3p6 3d10. 3 The 2p orbitals have different energies but same shape. A 1 and 2 B 1 only C 1 and 3 D 3 only 3 Use of the Data Booklet is relevant to this question. Substances exhibit magnetic behaviour based on the presence or absence of unpaired electrons. Paramagnetic species contain one or more unpaired electrons, making them slightly attracted to an external magnetic field. Diamagnetic species have all their electrons paired, causing them to be weakly repelled by a magnetic field. Which of the following species is diamagnetic? A Ti2+ B Zn2+ C Cu2+ D Fe2+ 4 Which species contains only covalent and dative bonds within itself? A Al2O3 B SO3 C NH4Cl D H3O+

3 © Raffles Institution 2025 8873/01/S/25 [Turn Over 5 The reactivity of halogen derivatives can be observed in the following reaction. CH3CH2X + OH− ⎯→ CH3CH2OH + X− (X = Cl or Br) Which statement explains why the reaction takes place more rapidly for bromoethane than for chloroethane? 1 Permanent dipole-permanent dipole forces between chloroethane molecules are stronger than those between bromoethane molecules. 2 C−Cl bond is more polar than C−Br bond. 3 C−Cl bond is stronger than C−Br bond. A 1 only B 2 only C 2 and 3 D 3 only 6 Liquefying gases is a common practice to reduce their volume, allowing for easy transportation and efficient storage. Which statement correctly explains why O2 is easier to liquefy than N2? A O2 has a lower boiling point than N2. B O2 has a longer bond length than N2. C O2 has a double bond but N2 has a triple bond. D O2 has stronger instantaneous dipole-induced dipole forces than N2. 7 Substance S • is a solid at room temperature • does not conduct electricity in solid and molten state • is insoluble in water. What could be the structure of S? A ionic B metallic C giant molecular D simple molecular

4 © Raffles Institution 2025 8873/01/S/25 [Turn Over 8 Use of the Data Booklet is relevant to this question. Chlorine gas is a severe irritant to the eyes. The maximum safe level of tolerance of chlorine gas in air is 0.005 mg dm−3. How many molecules of chlorine gas are present in 1 dm3 of air at this toleration level? A 23 0.005 × 716 10 B 230.005 × 6 × 10 × 271 C 230.005 1 × 6 × 101000 71  D 230.005 × 71 6 × 101000  9 Use of the Data Booklet is relevant to this question. The complete combustion of 0.0050 mol of hydrocarbon Q requires 0.720 dm 3 of oxygen measured at r.t.p. 0.36 g of water is produced. What is the molecular formula of Q? A C2H4 B C3H4 C C4H8 D C6H8 10 Use of the Data Booklet is relevant to this question. When 1.0 g of magnesium is added to 100 cm3 of 1.0 mol dm−3 dilute hydrochloric acid in a insulated container, the temperature of the solution rose from 20.0 C to 35.0 C. Assume that the specific heat capacity of the solution is 4.18 J g−1 K−1 and the density of the solution is 1.00 g cm−3. Mg(s) + 2HCl(aq) ⎯→ MgCl2(aq) + H2(g) What is the enthalpy change per mole of H2 produced? A −1.53 kJ mol−1 B −62.7 kJ mol−1 C −152 kJ mol−1 D −154 kJ mol−1

5 © Raffles Institution 2025 8873/01/S/25 [Turn Over 11 The reaction pathway diagram for a two-step reaction is shown below. step 1: W ⇌ X step 2: X ⎯→ Y Which statement about the reaction is correct? A The activation energy for the forward reaction of step 1 is higher than that of step 2. B Step 2 is more exothermic than step 1. C The activation energy for the backward reaction of step 1 is +66 kJ mol–1. D The enthalpy change of reaction for the conversion of W to Y is −113 kJ mol−1. 12 An energy cycle is shown. What is the average value for the S−F bond energy? A 148 kJ mol−1 B 276 kJ mol−1 C 296 kJ mol−1 D 592 kJ mol−1 progress of reaction energy / kJ mol–1 55 121 168 W X Y S(g) + 4F(g) + F2(g) S(g) + 6F(g) SF4(g) + F2(g) SF6(g) − 434 kJ mol−1 +158 kJ mol−1

6 © Raffles Institution 2025 8873/01/S/25 [Turn Over 13 The standard enthalpies of formation for the following compounds are given in the table below. compound ∆Hf / kJ mol−1 C6H12O6(s) −1273 CO2(g) −394 H2O(l) −286 Calculate the enthalpy change for the combustion of 1 mole of glucose in the given equation. C6H12O6(s) + 6O2(g) ⎯→ 6CO2(g) + 6H2O(l) A −593 kJ mol−1 B −1953 kJ mol−1 C −2807 kJ mol−1 D −5353 kJ mol−1 14 Melphalan is a drug used in chemotherapy. When dissolved in blood, the rate of elimination of Melphalan from the body follows a first-order kinetics. It takes 4 hours for the concentration of Melphalan in a patient’s blood to decrease from 100 µg cm-3 to 25 µg cm-3. How long does it take for the concentration of Melphalan in the blood of the same patient to decrease from 200 µg cm-3 to 25 µg cm-3? A 8 hours B 6 hours C 4 hours D 2 hours 15 Which statement does not explain why the introduction of a catalyst leads to an increase in the rate of a reaction? A The rate constant increases. B The catalyst provides an alternative pathway. C The reactant molecules move more quickly. D The proportion of collisions that is successful between the reactant molecules is higher.

7 © Raffles Institution 2025 8873/01/S/25 [Turn Over 16 Which statements about the conditions used in Haber process are correct? 1 An iron catalyst is used to increase the equilibrium yield of ammonia. 2 A pressure of 200 atmospheres is used because a high pressure will favour the side of the equilibrium with the greater number of molecules. 3 A temperature of 400 C to 500 C is used to increase the rate of reaction. 4 A temperature of 400 C to 500 C is used because a high temperature will increase the equilibrium yield of ammonia. A 1, 2 and 3 B 3 only C 1, 3 and 4 D 2 and 4 only 17 Initially, 4.0 mol o