TMJC 2025 H1 Chem P1 Answer

___________________________________________________________________ H1 CHEMISTRY 8873/01 Paper 1 Multiple Choice 25 September 2025 1 hour Additional materials: Multiple Choice Answer Sheet Data Booklet _________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write in soft pencil. There are thirty questions in this section. Answer all questions. For each question, there are four possible answers labelled A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read very carefully the instructions on the use of Answer Sheet. You are advised to fill in the Answer Sheet as you go along; no additional time will be given for the transfer of answers once the examination has ended. 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 12 printed pages. Use of Answer Sheet Ensure you have written your name, class, date and subject on the Answer Sheet. Shade the last four digits of your centre/index number on the Multiple Choice Answer Sheet. (e.g. if your centre/index number is 30541234, shade 1234). Use a 2B pencil to shade your answers on the Answer Sheet; erase any mistakes cleanly. Multiple shaded answers to a question will not be accepted. TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry 2 Atoms of elements from hydrogen to zinc have specific electronic arrangements. Which statement is correct? A The shell with principal quantum number 3 can hold a maximum of 8 electrons. B The electrons always occupy the highest energy orbitals available. C The order of filling the orbitals is 1s, 2s, 2p, 3s, 3p, 3d, 4s. D In some atoms, electrons occupy the fourth shell even though the third shell is not full. Answer: D Transition elements to fill 4s subshell before 3d. Examples include Sc: [Ar]3d 14s2 Ti: [Ar]3d 24s2 1 The relative atomic mass of antimony, which consist of the isotopes 121Sb and 123Sb, is 121.8. Calculate the percentage of 123Sb in the isotopic mixture. A 40% B 45% C 50% D 60% Answer: A Let the percentage of 123Sb in the isotopic mixture be x% 𝑥 100 123 + 100 − 𝑥 100 121 = 121.8 123x -121x = 80 x = 40% 3 Elements E and F have the following successive ionisation energies in kJ mol−1. 1st 2nd 3rd 4th 5th 6th 7th E 580 1800 2700 11600 14800 18400 23300 F 1310 3400 5300 7500 11000 13300 20300 What could be the formula of the compound formed by these two elements? A EF3 B E2F3 C E3F2 D E4F3 Answer: B Element E is from Group 13: largest IE difference between 3 rd and 4th IE Element F is from Group 16: largest IE difference between 6 rd and 7th IE Compound formed: E 2F3 eg: Al2O3

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry 4 Which combination correctly represents the shape around the central atom in each of the species? SH2 BF3 NCl3 A linear trigonal pyramidal trigonal planar B linear trigonal planar trigonal pyramidal C bent trigonal pyramidal trigonal planar D bent trigonal planar trigonal pyramidal Answer: D SH2: bent BF3: Trigonal planar NCl3: Trigonal pyramidal 5 Gases can be liquefied under certain conditions. Which statements about liquefaction of a non-polar gas are correct? 1 Some gases can be liquefied at room temperature by applying pressure. 2 The strength of the intermolecular forces is negligible at high pressure. 3 The strength of the intermolecular forces becomes more significant at low temperature. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 Answer: B Applying pressure brings molecules closer and hence intermolecular forces becomes more significant for liquefaction to take place. At low temperature, molecules have lower kinetic energy, move slower and hence intermolecular forces becomes more significant for liquefaction to take place. [Note that the forces are not getting stronger, merely more significant in comparison to the decreased kinetic energy.]

4 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry 6 Ammonium lauryl sulfate (ALS) is an anionic surfactant found primarily in shampoos and body–wash as a foaming agent. ALS is soluble in both water and oil. The structure of ALS is as follows. Which statement is incorrect about ALS? A It is soluble in oil, due to the presence of compatible intermolecular instantaneous dipole–induced dipole interactions with oil molecules. B It is soluble in water, due to the presence of ion–dipole interactions with water molecules. C It has a high melting and boiling point due to the hydrogen bonding between the particles. D The pi bond in S=O is due to the side-on overlap of the orbitals. Answer: C A is correct. The weak instantaneous dipole-induced dipole attractions between the non -polar hydrocarbon section of ALS is similar in strength / compatible to the weak instantaneous dipole -induced dipole attractions between the non -polar oil molecules. B is correct. The presence of anions and cations in ALS allows for the formation of ion –dipole interactions, which result in the release of sufficient energy to cause the detachment of ions from the giant ionic lattice structure for solvation. C is incorrect. ALS does not form intermolecular hydrogen bonding. Instead it is the ionic bonding between the oppositely charged ions that brings about a high melting and boiling point. D is correct as there is pi bond is formed from side-on overlap. 7 Consecutive elements L, M and N are in Period 3 of the Periodic Table. Element M has the lowest melting point and the highest first ionisation energy of these three elements. What are the identities of L, M and N? A sodium, magnesium, aluminium B magnesium, aluminium, silicon C aluminium, silicon, phosphorus D silicon, phosphorus, sulfur

5 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry Answer: D P has the lowest melting point as it consists of id -id attractions with smaller electron cloud. The 1 st IE is the largest as it is from group 15 compared to group 14 (Si) and group 16 (S). 8 Which statement about Period 3 elements is true across the period? A The pH of the oxides in water decreases. B The solubility of the oxides in water increases. C The melting points of the elements decreases. D The electrical conductivity of the elements decreases. Answer: A Metallic oxides Al2O3 and SiO2 Non-metallic oxides Basic Not soluble in water acidic pH>7 pH = 7 pH<7 9 How do the following properties for Group 1 elements change down the group? reducing power ionic radius ionisation energy A increases increases decreases B increases decreases increases C decreases decreases increases D decreases increases decreases Answer: A Reducing Power: As the atomic size increases down the group, the attraction of nucleus for electrons decreases and hence ease of losing electrons increases. Thus the reducing power increases as well. Ionic Radius: Down the group, each element has 1 more principal quantum shell and hence bigger ionic radius. Ionisation Energy: As the atomic size increases down the group, the attraction of nucleus for electrons decreases and hence ease of losing electrons increases. Thus the energy needed to remove electrons(ionisation energy) decreases.

6 Tampines Meridian Junior College 2025 JC2 Pre