2024 Prelims ASRJC H2 Chem P3 (QP)

ASRJC JC2 PRELIM 2024 9729/03/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2024 JC 2 PRELIMINARY EXAMINATION NAME:______________________________ ( ) CLASS: 24 / _____ CHEMISTRY 9729/03 Paper 3 Free Response Questions 13 September 2024 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and register number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, 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. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Paper 3 A1 / 21 Paper 1 (15%) / 30 A2 / 16 Paper 2 (30%) / 75 A3 / 23 Paper 3 (35%) / 80 B4* / 20 Paper 4 (20%) / 55 B5* / 20 Percentage *Circle the question you have attempted Grade This document consists of 28 printed pages.

2 ASRJC JC2 PRELIM 2024 9729/03/H2 Section A Answer all the questions in this section. 1 (a) (i) State the full electronic configuration of an Fe2+ ion. [1] (ii) Explain why Fe 2+(aq) ions are green, whereas aqueous Group 2 metal ions are not coloured. [4] …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... (b) Iron(II) carbonate can be prepared by reacting solutions of the two ions, Fe 2+(aq) and CO32–(aq). Explain why the same method cannot be used to prepare solid iron(III) carbonate. [2] ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. …………………………………………………………………………………………………………..

3 ASRJC JC2 PRELIM 2024 9729/03/H2 [Turn over (c) The minimum temperature to decompose some Group 2 carbonates increases down the group as shown in Table 1.1. Table 1.1 Group 2 carbonate Minimum temperature of decomposition / oC MgCO3 350 CaCO3 840 SrCO3 1289 BaCO3 1360 When heated, solid copper(II) carbonate behaves in a similar way to the Group 2 carbonates. (i) Write an equation for the thermal decomposition of copper(II) carbonate. [1] (ii) Use data from the Data Booklet and Table 1.1 to suggest a minimum temperature at which pure copper(II) carbonate decomposes. Explain your reasoning. [3] …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………...

4 ASRJC JC2 PRELIM 2024 9729/03/H2 (d) The chemistry and coordination of cobalt( II) compounds are similar to those of copper( II) compounds with similar ligands. (i) When cobalt(II) nitrate, Co(NO3)2, is added to water, a pink solution of G is formed. When aqueous sodium hydroxide is added to solution G, a blue precipitate H is observed. Precipitate H dissolves when excess aqueous ammonia is added to form a brown solution I. Nitrogen and hydrogen are the only other elements in the octahedral cobalt-containing complex in I. Identify the complex species in G, H and I. For each of the reactions to form H and I, identify the type of reaction and give relevant chemical equations. [4] (ii) Addition of concentrated hydrochloric acid to pink solution G forms a blue solution J. Solution J turns pink again when water is added to it. With the aid of a balanced equation, explain these observations. [2] (iii) Salt K has the molecular formula CoN5H17OCl3 (Mr = 268.4). It has one or more ligands which is similar to those found in complex species G, H and J. When 1.00 g of salt K is dissolved in water, the resulting solution required 22.40 cm3 of 0.50 mol dm–3 silver nitrate solution for complete reaction. Calculate the number of moles of free chloride ions per mole of K and give the structural formula of the complex ion in K. [2] …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………...

5 ASRJC JC2 PRELIM 2024 9729/03/H2 [Turn over …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... (e) The ethanedioate ion, C2O42–, can act as a bidentate ligand. (i) Explain what is meant by a ligand