NYJC_Prelim_CHEM_P3_ans

1 [Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9647/03 Paper 3 Free Response 21 September 2016 2 hours Candidates answer Section A on the Question Paper Additional Materials: Writing Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. 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 any four questions. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answ ers. 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. Section B Answer all questions on separate answer paper. For Examiner’s Use Section A 1 2 3 4 5 Total This document consists of 13 printed pages and 1 blank page.

2 H2 Chemistry 9647/03 NYJC J2/16 PX [Turn Over Answer any four questions. 1(a) Copper(I) sulfate, Cu 2SO4, can be made from copper(I) oxide under non -aqueous conditions. On adding this salt to water, it immediately undergoes a disproportionation reaction. (i) Suggest, with a reason, the colour of copper(I) sulfate. [2] (ii) Using suitable data from the Data Booklet , explain why the disproportionation reaction occurs, and write an equation for it. [3] (b) Palladium(II) salts can form square planar complexes. Successive addition of ammonia and hydrogen chloride to an aqueous palladium(II) salt produces, under different conditions, three compounds with empirical formula PdN 2H6Cl2. Two of these, A and B, are non-ionic, with Mr = 211. A has a dipole moment, whereas B has none. The third compound, C, is ionic, having Mr = 422, and contains palladium in both its cation and anion. For each A, B and C, deduce a structure that fits the above data , explaining your reasons fully. [6] (c) Benzene ring is often represented as a structure that has a ring within the hexagon. Alternatively, chemists have also represented the structure of benzene in the following forms, known as resonance structures. Benzene (two resonance forms) The resonance relationship is indicated by the double headed arrow between them. The only difference between resonance forms is the placement of the pi electrons and non-bonding electrons. Most aromatic compounds undergo electrophilic substitution. However aryl halides undergo a limited number of substitution reactions with strong nucleophiles. An example of a reaction is as follows: XA NuA Nu + X where A is an electron withdrawing group and X is a halogen The m