VJC JC2 H1 Prelim P1 QP with Ans

1 © VJC 2025 8873/01/PRELIM/25 [Turn over VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CHEMISTRY ANSWER 8873/01 Paper 1 Multiple Choice 19 September 2025 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name and CT group on the Answer Sheet. 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. A Data Booklet is provided. 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 10 printed pages.

2 © VJC 2025 8873/01/PRELIM/25 For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 9Be is used in the production of ‘fast neutrons’. How many neutrons are present in 0.09 g of 9Be? [L = Avogadro constant] A 0.04 L B 0.05 L C 0.09 L D 0.45 L Answer: B Amount of 9Be = 0.09 / 9 = 0.01 mol No. of 9Be atoms = 0.01 x L = 0.01 L Mole ratio of 9Be : neutrons 1 : (9–4) = 5 No. of neutrons = 0.01 L x 5 = 0.05 L 2 The table below shows the fifth, sixth, seventh, eighth and ninth ionisation energies of elements L and M in kJ mol–1. Elements L and M are found in period 3. 5th 6th 7th 8th 9th L 6270 21300 25400 29900 35900 M 6540 9360 11000 33600 38600 Given that all the atoms have at least an octet configuration, what could not be the formula of the compound formed by these two elements? A LM5 B LM4+ C LM3 D LM2 Answer: D For element L, there is a large increase from the 5th to the 6th ionisation energy, indicating that the 6th electron is removed from the next inner quantum shell. This means that the element has 5 valence electrons and is in group 15. The element is Phosphorous. For element M, there is a large increase from the 7th to the 8th ionisation energy, indicating that the 8th electron is removed from the next inner quantum shell. This means that the element has 7 valence electrons and is in group 17. The element is Chlorine. Since elements L and M are in the same period and element L has less valence electrons, element L is less electronegative than element M as electronegativity increases across the period. Hence, element L should be the central atom in the compound. Option A (incorrect): LM5 is possible as L is in period 3 and have vacant and energetically accesible d orbital to expand its octet structure.

3 © VJC 2025 8873/01/PRELIM/25 [Turn over Option B (incorrect): LM4+ is possible. Since L is less electronegative than M, the lost of one electron was from element L to form a positively-charged ion. Option C (incorrect): LM3 is possible as all the atoms fulfil at least an octet structure. Option D (correct): LM2 is not possible as the central L atom would be electron-deficient and not fulfil at least an octet structure. 3 The diagram shows the structure of a pyruvic acid. pyruvic acid What set of bond angles are present in pyruvic acid? A 120o, 109o, 105o B 120o, 105o, 90o C 180o, 120o, 109o D 180o, 120o, 90o Answer: A L M M x x• x• xx • • • • • • • • • • • • M L M M x• x• x• xx • • • • • • • • • • • • • • • • • • M L M M x• x• x• x• • • • • • • • • • • • • • • • • • • M • • • • • • + M L M M x• • • • • • • • • • • • • • • • • • • M • • • • • • M • • • • • •

4 © VJC 2025 8873/01/PRELIM/25 4 Which statements about water are due to its ability to form hydrogen bonds? 1 Liquid water is denser than ice. 2 Water has a significantly higher boiling point than methane , CH 4, even though both compounds have similar relative molecular masses. 3 The high surface tension of water enables some insects to walk on the surface of the ponds. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 and 3 only Answer: A Option 1 (correct): The hydrogen bonds in ice results in a rigid, highly ordered and open structure where the water molecules are more spaced out as compared to liquid water. Option 2 (correct): The hydrogen bonds in water is much stronger than the id-id interaction in methane, resulting in a stronger interaction between molecules . More energy is required to break the interaction between molecules and this lead to a higher boiling point. Option 3 (correct): The strong hydrogen bonds in water do not break when small insects exert a force on it. 5 Synthetic rubber is commonly produced from the monomer buta-1,3-diene. buta-1,3-diene What are the numbers of σ and 𝜋 bonds present in one molecule of buta-1,3-diene? σ 𝜋 A 6 4 B 7 4 C 8 2 D 9 2 Answer: D Each single bond is a sigma bond, and each double bond is made up of a sigma and a pi bond. Hence there are a total of 9 sigma bonds and 2 pi bonds.

5 © VJC 2025 8873/01/PRELIM/25 [Turn over 6 Which of the following molecules is not polar? A CCl3F B NOCl C SF4 D BF3 Answer: D A non-polar molecule have zero overall net dipole moment. no. of bond pairs around central atom no. of lone pairs around central atom shape polarity CCl3F 4 0 tetrahedral polar NOCl 2 1 bent polar SF4 4 1 see-saw polar BF3 3 0 trigonal planar non-polar Structure of nitrosyl chloride: 7 What is the definition of an Arrhenius base? A a substance that accepts hydrogen ions B a substance that donates a 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 Answer: C An Arrhenius base dissociates in water to give hydroxide ions by definition. 8 A solid base is added to a small lake to reduce the effects of acid rain. The pH of the water in the lake changes from 4 to 6. What is the change in [H+] of the water in the lake? A It is 100 times smaller. B It halves. C It is 100 times greater. D It doubles. Answer: A At pH 4, [H+] = 10–4 At pH 6, [H+] = 10–6 Therefore [H+] is 100 times smaller.

6 © VJC 2025 8873/01/PRELIM/25 9 Which row gives the correct expression for Kw and for the Kb of ammonia, NH3? Kw Kb(NH3) A Kw = [H+][OH–] Kb = [H+][NH2–]/[NH3] B Kw = [H+][OH–] Kb = [OH–][NH4+]/[NH3] C Kw = [H+][OH–]/[H2O] Kb = [H+][NH2–]/[NH3] D Kw = [H+][OH–]/[H2O] Kb = [OH–][NH4+]/[NH3] Answer: B H2O(l) ⇌ H+(aq) + OH−(aq) Kw is also known as the ionic product of water. Kw = [H+][OH−] NH3(g) +H2O(l) ⇌ NH4+(aq) + OH−(aq) Kb is also known as the base dissociation constant. By treating ammonia as a base, Kb = [NH4+][OH−]/[NH3] 10 Use of the Data Booklet is relevant to this question. Which chemical formula is not possible for phosphorous? A P4O6 B P4O10 C PO2 D PO3 Answer: D Phosphorous is in Group