TMJC_2025_H1 Chem_P2_Answer

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] 2s22p63s23p1 Extent of deflection  q m +1.7° +5° = (+𝑋 27 ) (+3 27) x = 1.02 = 1 to nearest whole no. source – + +5 27Al 3+ +1.7 27Al x+ 2s22p6

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. ……………………………………………………………………