TMJC 2025 H1 Chem P2 QP

CANDIDATE NAME CIVICS GROUP ______________________________________________________________________________ H1 CHEMISTRY 8873/02 Paper 2 Structured Questions 2 September 2025 2 hours Candidates answer on the Question Paper. Additional materials: Data Booklet ______________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name and civics group in the spaces provided at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all the questions. Section B Answer one question. 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. ________________________________________________________________________________________ This document consists of 25 printed pages and 1 blank page. Examiner’s Use Paper 1 MCQ / 30 Paper 2 Section A Q1 / 10 Q2 / 13 Q3 / 14 Q4 / 11 Q5 / 12 Section B Q6 / 20 Q7 / 20 / 80 Total / 100 Grade TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry Section A Answer all the questions in this section in the spaces provided. 1 (a) Aluminium is the most abundant Group 13 element. Compounds, such as Al(OH)3, can be used for different purposes such as food additives and pharmaceuticals. (i) Write down the electronic configurations for Al and Al3+. Al : 1s2 ………………………………. Al3+ : 1s2 ………………………………. [2] (ii) In an experiment, a sample of aluminium was vapourised, ionised and passed through an electric field. It was observed that a beam of 27Al3+ ions gives an angle of deflection of +5 as shown in Fig. 1.1 below. Fig. 1.1 Using the same set-up, another aluminium atom was vaporised and ionised to give an unknown ion, 27Alx+. Based on the information given, determine the value of x. [2] source – + +5 27Al 3+ +1.7 27Al x+

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry [Turn over (iii) Al3+ is a commonly formed ion of aluminium. However, under special conditions, it can briefly exist as Al+ and Al2+ ions. Complete Table 1.1 for each subatomic particle of the two ions. Table 1.1 [2] (b) Both Al(OH)3 and Mg(OH)2 are antacids. They are used to treat symptoms of increased stomach acid, such as heartburn and acid indigestion. (i) Suggest why the melting point of Al(OH)3 is likely to be higher than that of Mg(OH)2. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. …………………………………………………………………………………………… [2] (ii) Based on experimental data, the melting point of Al(OH)3 is found to be lower than that of Mg(OH)2. Suggest a possible reason for this. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. …………………………………………………………………………………………… [1] (iii) Mg(OH)2 is sparingly soluble in water. Complete and label the diagram, showing clearly the interaction between Mg2+ ion and one water molecule, to illustrate why Mg(OH)2 can dissolve in water. [1] [Total: 10] number of protons number of neutrons number of electrons Al13 27 + Al13 27 3+ Mg2+

4 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry 2 Vitamin C, also known as ascorbic acid (C 6H8O6), is an essential nutrient for humans. It functions as an antioxidant and supports the immune system. The structure of ascorbic acid is shown below. ascorbic acid, C6H8O6 (a) Name the functional groups, excluding hydroxy group (−OH), present in ascorbic acid. ……………..…………………………………………………………………………………… [1] A student carried out an experiment to verify the ascorbic acid content stated on an orange juice carton. The label claims that the orange juice contains 120 mg of ascorbic acid per 100 cm³. The student carried out the following titration to verify if the claim is true. In this experiment, 25.0 cm³ of the orange juice was used. The procedure was carried out as follows: 1. excess potassium iodate (KIO₃) was reacted with potassium iodide (K I) in an acidic medium. 1.50 x 10-4 mol of iodine (I2) was produced as a result of this reaction. IO3⁻ + 5I⁻ + 6H⁺ 3I2 + 3H2O 2. The iodine (I2) produced reacted with ascorbic acid solution. C6H8O6 + I2 C6H6O6 + 2HI 3. The excess unreacted iodine ( I2) required 29.60 cm³ of 5.00 x10 -4 mol dm⁻³ sodium thiosulfate for titration to reach the end-point. I2 + 2S2O3²⁻ 2I⁻ + S4O6²⁻ (b) (i) Calculate the amount of C6H8O6 that is present in 25.0 cm 3 of the orange juice sample. [2] ⎯⎯ → ⎯⎯ → ⎯⎯ →

5 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry [Turn over (ii) Given that the molar mass of ascorbic acid is 176 g mol −1, calculate the mass of ascorbic acid, in mg, per 100 cm 3 of orange juice. Based on your result, deduce whether the manufacturer’s claim is accurate. [2] (c) (i) Draw a dot-and-cross diagram of IO3⁻ ion. [1] (ii) State and explain, with reference to VSEPR theory, the shape and bond angle of IO3⁻ ion. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. …………………………………………………………………………………………… [2]

6 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry (d) (i) When the chlorides of Period 3 elements are added to water, they produce solutions with different pH values. Complete Table 2.1 below. Table 2.1 Compound pH NaCl MgCl2 AlCl3 SiCl4 [2] (ii) Describe what happens when AlCl3 is added to water. Include equations for any reaction(s) that occur. ………………………………………………………………………………………………. ……..……………………………………………………………………………………….. ………………………………………………………………………………………..…….. ………………..…………………………………………………………………………….. …….…………………………………………………………………………………….. [2] (iii) Gallium and aluminium are elements in Group 13 of the Periodic Table. Gallium oxide, Ga2O3 has similar acid-base behaviour as aluminium oxide. Write a balanced equation for the reaction that occurs when Ga 2O3 reacts with NaOH(aq). ………………………………………………………………………………………………. …………………………………………………………………………………………… [1] [Total:13]

7 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry [Turn over 3 (a) Poly methyl methacrylate (PMMA) is a commonly used material in modern dentistry, such as in the fabrication of dental prosthetics. PMMA can be repeatedly softened by heating and solidified by cooling, making it easily moldable into various dental appliances. The repeat unit of PMMA is shown below. C CH2 C O O CH3 CH3 n (i) State the type of polymerisation used to make PMMA and draw the structure of the monomer used to make this polymer. Type of polymerisation: ………………………………………………………….……… Monomer: [2] (ii) Based on the polymer’s behaviour upon heating, state whether it is a thermoplastic or a thermoset. …………………………………………………………………………………………… [1] (iii) Chemical agents can be added to PMMA to form cross -linked PMMA polymers which are used in dental fillings. Explain why cross-linked polymers are suitable for use in dental fillings. ………………………………………………………………………………………………. …………………………………………………………………………………………… [1]

8 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H1 Chemistry (iv) In other uses, 1,4-butanediol can form hydrogen bonds with PMMA