2025 SAJC H1 Chem Prelim P1 Questions

1 ST ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS HIGHER 1 CANDIDATE NAME CLASS 2 4 S CHEMISTRY Paper 1 Multiple Choice Candidate answer on the Optical Answer Sheet Additional Materials: Data Booklet 8873/01 18 September 2025 1 hour READ THESE INSTRUCTIONS FIRST 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 Optical Answer Sheet. 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 16 printed pages (including this cover page).

2 1 Which statement is correct? A One mole of a compound is the amount that contains the same number of atoms as there are in 12.0 g of C12 . B The relative isotopic mass of beryllium-9 is given by the following expression. average mass of all isotopes of beryllium 1 12 the mass of one atom of C12 C 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 C12 D The relative molecular mass of Q is given by the following expression. average mass of one atom of Q 1 12 the mass of one atom of C12 2 10 cm 3 of a gaseous hydrocarbon, C xHy, was exploded with an excess of oxygen. There was a contraction of 40 cm3. When the product s were treated with aqueous sodium hydroxide, there was a further contraction of 50 cm3. All gas volumes are measured at room temperature and pressure. What is the molecular formula of the hydrocarbon? A C4H8 B C4H10 C C5H10 D C5H12

3 3 In which row are X and Y atoms or ions of different isotopes of the same element? X Y Number of electrons charge Nucleon number Number of electrons charge Nucleon number A 3 +3 12 9 –3 12 B 8 0 16 11 –1 19 C 10 +1 23 10 +1 24 D 18 –3 31 12 +3 31 4 Which particle will deflect the most when moving with the same speed through an electric field? A Li7 + B B11 3+ C F19 − D P31 3− – Beam of ionic species +

4 5 Use of the Data Booklet is relevant to this question. The table shows the fifth, sixth, seventh, eighth and ninth ionisation energies (IE) of an element in the third period. Element 5th 6th 7th 8th 9th IE/ kJmol–1 13352 16611 20115 25491 28934 What element has these ionisation energy values? A P B S C Cl D Ar 6 Which molecules are not polar? 1 H2S 2 CS2 3 SO2 4 SF6 A 1 and 2 B 2 and 4 C 3 and 4 D 4 only

5 7 The diagram shows the structure of part of a crystal of ice. Which statement is correct? A The hydrogen bonds, shown by the dotted lines, are stronger than the O −H covalent bonds. B The weaker covalent bonds in ice causes it to be less dense than water. C All the bond angles surrounding each oxygen atom are 120. D Each oxygen can form 2 hydrogen bonds. 8 Some information about some of the elements of Period 5 of the Periodic Table is shown: element Rb Sr In Sn Sb Te I Xe Electrical conductivity high high high high high semi- conductor zero zero Boiling point / K 961 1650 2300 2540 1650 1260 457 165 Which statement about these elements is correct? A Both I and Xe have simple molecular structures. B Elements from Rb to Te have giant metallic structures. C There are less elements with metallic structures in Period 5 than in Period 3. D Sr has higher boiling point than Rb because of higher charge density.

6 9 A mixture consisting of gaseous compounds, S, T, U and V, is slowly cooled. Gaseous Compound Mr Compound S 72 CH3CH2COCH3 T 74 CH3CH2CH(OH)CH3 U 72 (CH3)4C V 72 CH3CH2CH2CH2CH3 In which order, from first to last, will the compounds condense to form their liquids? A T → S → V → U B U → V → S → T C S → T → V → U D V → U → S → T 10 In a chlorine molecule, C l2, the two chlorine atoms are held together by a single covalent bond. The bond energy is 244 kJ mol–1. The bond length is 0.198 nm. What do the terms bond energy and bond length mean? bond energy bond length A the energy needed to make one mole of bonds the distance between the outer shells of the two bonded atoms B the energy needed to make one mole of bonds the distance between the nuclei of the two bonded atoms C the energy needed to break one mole of bonds the distance between the outer shells of the two bonded atoms D the energy needed to break one mole of bonds the distance between the nuclei of the two bonded atoms

7 11 The standard enthalpy change of combustion of ethane is –1560 kJ mol–1. C2H6 (g) + 7 2 O2 (g) → 2CO2 (g) + 3H2O (l) Values of the relevant average bond energies are given in the table. Bond C–H C–C C=O O–H O=O Average bond energy/ kJ mol–1 410 350 805 460 496 What is the value for the enthalpy change of vaporisation of water? H2O (l) → H2O (g) A – 126 B – 42 C + 42 D + 126 12 Which of the following reactions are exothermic? 1 MgCO 3 (s) → MgO (s) + CO 2 (g) 2 NaOH (aq) + HC l (aq) → NaC l (aq) + H 2O (l) 3 C2H4 (g) + 3O 2 (g) → 2CO 2 (g) + 2H 2O (l) A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only

8 13 This question refers to ‘reaction Z’ in which compound P is converted into compound R. reaction Z P R This reaction can be broken down into two stages. stage 1 P Q stage 2 Q R The energy profile of the reaction Z is shown. Which rows about the magnitudes of activation energy and enthalpy chage of reaction are correct? magnitude of activation energy magnitude of enthalpy change of reaction 1 for reaction Z ∆E1 ∆E5 2 for stage 1 ∆E1 ∆E3 3 for stage 2 ∆E4 ∆E7 A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only

9 14 The half -life of the first -order gaseous reaction in which M 2 molecules become converted into M atoms is 30 minutes. 1 mol of M 2 is put into a sealed vessel at pressure p. What will be true when 75% of M2 has been converted into M atoms? 1 Three half-lives have passed. 2 60 minutes have elapsed. 3 1.5 mol of M have been formed. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only 15 Curves 1 and 2 show the Boltzmann distributions for identical compositions of a reaction mixture which occur at different temperatures. Which statement is correct? A Curve 1 applies to the faster reaction and point W indicates particles with lower energy than point Z. B Curve 1 applies to the faster reaction and point W indicates particles with higher energy than point Z. C Curve 2 applies to the faster reaction and point X indicates particles with lower energy than point Y. D Curve 2 applies to the faster reaction and point X indicates particles with higher energy than point Y.

10 16 The graph shows how the initial rate of reaction varies for an enzyme catalysed reaction as the substrate concentration changes. Which of the statements correctly describe the situation when [substrate] = x? 1 The initial rate of reaction is affected by increasing [substrate]. 2 The order of reaction with respect to [substrate] is 1. 3 There are no more enzyme active sites available. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only 17 A sample of 1 mole of XY was placed in an empty 1 dm 3 container and allowed to reach equilibrium according to the following equation. 2XY (g) X2 (g) + Y2 (g) At equilibrium, x mol of the XY had dissociated. What is the value of the equilibrium constant, Kp , at the temperature of the expe