2025 ASRJC Prelim H2Chem P3 QP

ASRJC JC2 PRELIM 2025 9729/03/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2025 JC 2 PRELIMINARY EXAMINATION NAME:_____________________________ _ ( ) CLASS: 25 / _____ CHEMISTRY 9729/03 Paper 3 Free Response Questions 29 August 2025 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 Pa pe r 3 A1 / 19 Paper 1 (15%) / 30 A2 / 18 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

2 ASRJC JC2 PRELIM 2025 9729/03/H2 This document consists of 28 printed pages.

3 ASRJC JC2 PRELIM 2025 9729/03/H2 [Turn over Section A Answer all the questions in this section. 1 (a) Transition elements have characteristic physical and chemical properties. (i) Explain what is meant by the term transition element. [1] (ii) Explain why the melting point and density of nickel is higher than that of calcium. [3] ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . (b) (i) A solution containing the [Ni(H2O)6]2+ complex ion is green. When 1,2 -diaminoethane, en , H 2NCH2CH2NH2, is added, the colour of the solution changes to purple. This is due to the formation of the [Ni(en)2(H2O)2]2+ complex ion. Explain why the two solutions are coloured, and why the colours are different. [3] (ii) [Ni(en)2(H2O)2]2+ complex ion can exist in three different forms where the ions differ in the spatial arrangement of the ligands around the central metal ion. Fig. 1.1 shows one of the isomers.

4 ASRJC JC2 PRELIM 2025 9729/03/H2 Ni N N OH2 N H2O N 2+ H2 H2 H2 H2 Fig 1.1 Draw another isomer and state the type of isomerism. [2] ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… .

5 ASRJC JC2 PRELIM 2025 9729/03/H2 [Turn over (c) When a sample of aqueous copper(II) sulfate was added to a small amount of aqueous ammonia, a blue precipitate A was formed. Upon adding excess aqueous ammonia, A dissolved, and a deep blue solution containing a complex ion, B, was formed. When another sample of aqueous copper( II) sulfate was added to concentrated hydrochloric acid, a yellow-green solution was formed. (i) Identify A and B and explain their formation. Include relevant equations. [4] (ii) Write an equation to explain the observation of the yellow-green solution. [1] ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… .

6 ASRJC JC2 PRELIM 2025 9729/03/H2 ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . ……………………………………………………………………………………………………………… . (d) Ruthenium can form complexes with ligands like H2NCH2CH2NH2 (represented as en) and NH3. Three redox systems involving ruthenium complex ions are shown in Table 1.1. Table 1.1 half-cell half equation A [Ru(H2O)6]3+ + e- ⇌ [Ru(H2O)6]2+ B [Ru(NH3)6]3+ + e- ⇌ [Ru(NH3)6]2+ C [Ru(en)3]3+ + e- ⇌ [Ru(en)3]2+ (i) Two electrochemical cells are set up to compare the standard electrode potential, Eo, of the three half-cells. Fig 1.2 shows the relative potential of each electrode. half-cell C half-cell B half-cell A half-cell C Fig 1.2 Using this information, state and explain the order of standard reduction potential, Eθ, for the three half-cells from the least negative to the most negative. [2] (ii) The standard electrode potential of the half-cell A is +0.25 V. An electrochemical cell was set up using half-cell A and a [Cu(NH3)4]2+/Cu half cell. Use data from the Data Booklet to calculate the Eo cell for this cell. [1] (iii) Write the overall equation for the reaction that occurs in the cell in (d)(ii). Using the Eocell you have calculated in (d)(ii), calculate a value of ∆Go for the cell reaction represented by your overall equation. [2]

7 ASRJC JC2 PRELIM 2025 9729/03/H2 [Turn over ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………