2025 H2 Chem Prelim P3 QP VJC

© VJC 2025 9729/03/PRELIM/2025 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729/03 Paper 3 Free Response 17 September 2025 2 hours Additional Materials: Data Booklet ________________________________________________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name and CT group on this cover page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all questions. Section B Answer one question. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 20 2 / 20 3 / 20 4 / 20 5 / 20 Total / 80 This document consists of 23 printed pages and 1 blank page.

2 © VJC 2025 9729/03/PRELIM/2025 Section A Answer all the questions in this section. 1 (a) Potassium is a highly reactive alkali metal that must be stored under oil, while copper is a much less reactive metal that resists corrosion. Table 1.1 shows the melting points of both metals. Table 1.1 Metal Melting point / C K 63.5 Cu 1085 (i) Copper does not react with most dilute acids, unlike potassium. With reference to the standard electrode potentials in the Data Booklet, explain why this is so. [2] (ii) Describe with the aid of a labelled diagram the structure of copper at room temperature. [2] (iii) Suggest why the melting point of copper is significantly higher than that of potassium as shown in Table 1.1. [2] (iv) Fig. 1.1 shows the first ionisation energies for the elements K to Cu. Fig 1.1 Explain why the first ionisation energy remains relatively constant from scandium to copper. [2] (v) Using your knowledge in the variation of first ionisation energy of the elements from potassium to copper, sketch the trend of the second ionisation energies on Fig 1.1. [1] ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... Ionisation energy / kJ mol−1 element

3 © VJC 2025 9729/03/PRELIM/2025 [Turn over ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ……………………………………………………………………………………………………….

4 © VJC 2025 9729/03/PRELIM/2025 (b) Copper is a transition element which form many different complexes. (i) Explain what is meant by the term transition element. [1] (ii) Copper(II) ions form a coloured complex with mercaptoethylamine, MEA, a bidentate ligand as shown in equation 1.1. equation 1.1 Cu2++ HSCH2CH2NH2 → [Cu(HSCH2CH2NH2)2]2+ MEA With reference to the complex in equation 1 .1, explain what is meant by the term ligand. [1] (iii) Explain why complexes of copper(II) are usually coloured. [3] ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………...

5 © VJC 2025 9729/03/PRELIM/2025 [Turn over (c) Polymerisation is a process where small molecules called monomers are combined to form larger polymer chains. Polymers are large molecules made of many repeat units. Thiirane, , can undergo free radical ring-opening polymerisation in the presence of a radical initiator, benzoyl peroxide and an excess of dodecanol, CH3(CH2)10CH2OH. Fig. 1.2 shows a proposed mechanism via three reactions. Reaction 1: Homolytic fission of a C –S bond in thiirane, generating a ‘double-ended’ free radical, •CH₂CH₂S•, that initiates a chain reaction. Reaction 2: A chain reaction occurs where the ring opens and units of •CH₂CH₂S• adds to a growing chain. Repeated steps involve production of other free radicals. Reaction 3: Termination with dodecanol to form CH3(CH2)10CH2–O–(CH2CH2S)n–H. Fig 1.2 (i) Use curly arrows to show the movement of electrons which occur in reactions 1 and reaction 2 on Fig. 1.2. [2] (ii) Suggest why thiirane undergoes the reaction more easily as compared to (CH3)2S. [1] ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………...

6 © VJC 2025 9729/03/PRELIM/2025 (d) The three compounds in Table 1.2 behave as monoprotic acids in aqueous solution. Table 1.2 name formula MEA NH₂CH₂CH2SH glycine NH₂CH₂COOH ethanolamine NH₂CH₂CH2OH Arrange the compounds in order of increasing acidity. Explain your answer. [3] ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………