2025 H1 Chem Prelim Paper 1 HCI

This document consists of 11 printed pages and 1 blank page. © Hwa Chong Institution 2025 8873/01/Prelim [Turn over HWA CHONG INSTITUTION C2 Preliminary Examination Higher 1 CANDIDATE NAME CT GROUP 24S CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 8873/01 22 September 2025 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid or tape. Write your name and CT group in the space provided at the top of this page. 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.

2 © Hwa Chong Institution 2025 8873/01/Prelim [Turn over 1 Use of the Data Booklet is relevant to this question. The table shows the fifth, sixth, seventh, eighth and ninth ionisation energies of an element in the third period. 5th 6th 7th 8th 9th ionisation energy / kJ mol–1 7200 8800 12 000 14 000 41 000 What element has these ionisation energy values? A P B S C Cl D Ar 2 The mineral pyrite contains sulfur and a transition metal in the fourth period. A sample of pyrite was analysed and four different atoms were identified; V, W, X and Y. The table shows information about the four types of atoms found in the sample. atom relative mass relative % abundance V 31.97 63.8 W 33.97 2.8 X 53.94 31.4 Y 55.95 2.0 What is the relative atomic mass of sulfur in the sample? A 32.05 B 32.10 C 32.97 D 39.40 3 Which row about  bonds and  bonds in hydrocarbons is correct?  bonds  bonds A can be formed by p orbitals but not s orbitals can be formed by s orbitals but not p orbitals B can be formed by s orbitals but not p orbitals can be formed by p orbitals but not s orbitals C can be formed by either s or p orbitals can be formed by p orbitals but not s orbitals D can be formed by either s or p orbitals can be formed by either s or p orbitals

3 © Hwa Chong Institution 2025 8873/01/Prelim [Turn over 4 What is the most likely bond angle at each nitrogen atom in the di-imine molecule, H–N=N–H? A 107o B 118o C 120o D 180o 5 Aluminium chloride, AlCl3, dimerises to form Al2Cl6. 2AlCl3 → Al2Cl6 Which statements are correct? 1 The geometrical arrangement of the atoms around aluminium changes from trigonal planar to tetrahedral. 2 Each aluminium atom contributes electrons to four covalent bonds. 3 There are 16 lone pairs of electrons in the Al2Cl6 molecule. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1 only 6 Metals have different electrical conductivities. Which row shows the correct order of increasing electrical conductivity of each pair of these metals? Period 3 Period 4 A Al < Mg Ca < Cu B Al < Mg Cu < Ca C Mg < Al Ca < Cu D Mg < Al Cu < Ca 7 What is the definition of an Arrhenius base? A a substance that accepts hydrogen ions B a substance that donates a lone pair of electrons C a substance that produces hydroxide ions in aqueous solution D a substance that readily reacts with an acid to form a salt and water only

4 © Hwa Chong Institution 2025 8873/01/Prelim [Turn over 8 When a weak base is added to a strong acid an increase in pH from pH 2 to pH 6 occurs at the end-point. What indicators would be suitable for use in a weak base and strong acid titration? indicator pH range 1 bromocresol green 3.8–5.4 2 cresol purple 7.4–9.0 3 methyl orange 3.1–4.4 4 phenol red 6.8–8.4 A 1 and 3 B 2 and 4 C 3 only D 4 only 9 At 50 oC, Kw = 5.48 × 10–14 mol2 dm–6. What is the pH and pOH of pure water at 50 oC? pH pOH A 7 7 B 6.6 7.4 C 6.6 6.6 D 7.4 6.6 10 The variation in melting points of Period 3 elements, from sodium to chlorine, can be explained in terms of the structure and bonding in the elements. Which statements are correct? 1 From sodium to magnesium to aluminium, t he melting points increase due to increasing charge density of the metal cations. 2 Silicon has a high melting point because it has a giant covalent structure. 3 From phosphorus to sulfur to chlorine, t he melting points increase due to increasing number of electrons in the molecules. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 only 11 Across a period, the elements show an increase in their maximum oxidation number in their oxides. What explains this? 1 an increase in ionisation energy 2 an increase in the number of electrons used for bonding 3 an increase in the number of electrons in the outer shell A 1, 2 and 3 B 2 and 3 only C 1 only D 2 only

5 © Hwa Chong Institution 2025 8873/01/Prelim [Turn over 12 Four separate experiments are performed. experiment 1 A spatula measure of Na2O is added to a test-tube of water and the tube is shaken. experiment 2 A spatula measure of MgO is added to a test-tube of water and the tube is shaken. experiment 3 A spatula measure of Al2O3 is added to a test-tube of water and the tube is shaken. experiment 4 A spatula measure of SiO2 is added to a test-tube of water and the tube is shaken. Which statements are correct? A There is no temperature change in any of the four experiments. B Two of the four experiments will result in a colourless solution with no undissolved solid. C The pH is the same in experiments 1 and 2 after shaking. D The pH is the same in experiments 3 and 4 after shaking. 13 Use of the Data Booklet is relevant to this question. The reaction of (CH 3)2N2H2 with N 2O4 has been studie d as a possible energy source for rockets. (CH3)2N2H2(l) + 2N2O4(g) → 2CO2(g) + 3N2(g) + 4H2O(g) 0.25 moles of (CH3)2N2H2 is completely combusted in N2O4. The product mixture is passed through saturated aqueous KOH and the final volume of gas, Q, is measured under room conditions. What is the volume of gas Q collected in this reaction? A 17 dm3 B 18 dm3 C 42 dm3 D 54 dm3 14 Use of the Data Booklet is relevant to this question. When bromide ions undergo oxidation to form bromine, electrons are lost. 2Br− → Br2 + 2e− The charge on one electron is –1.60 × 10–19 C, where C is the unit in coulombs. What is the charge lost, in coulombs, when 2.5 moles of bromine are formed from bromide ions? A 4.00 × 10–19 B 8.00 × 10–19 C 2.41 × 105 D 4.82 × 105

6 © Hwa Chong Institution 2025 8873/01/Prelim [Turn over 15 An energy cycle and some data are given. substance standard enthalpy change of combustion / kJ mol–1 C6H6(l) –3267 C(s) –394 H2(g) –286 What is the standard enthalpy change of formation, Hf o, of benzene, C6H6(l)? A +45.0 kJ mol−1 B –45.0 kJ mol−1 C +2587 kJ mol−1 D –2587 kJ mol−1 16 Use of the Data Booklet is relevant to this question. A student uses the apparatus shown to find the enthalpy change of combustion of an ester. 0.020 moles of ester was needed to raise the temperature of water in the beaker by 20 oC. The enthalpy change of combustion of the ester calculated from these results is –1200 kJ mol–1. What is the mass of water in the beaker, to the nearest 10 g? A 10 g B 290 g C 720 g D 1200 g beaker water thermometer spirit burner ester

7 © Hwa Chong Institution 2025 8873/01/Prelim [Turn over 17 Methane burns in oxygen to form carbon dioxide and water. The energy profile diagram is shown. Which statement about bond breaking and forming is correct