SAJC H2 Chem 2012 Prelim P2 QP

ST ANDREW’S JUNIOR COLLEGE JC2 Preliminary Examinations Chemistry 9647/02Higher 2 Paper 2 10 September 2012 2 hours Candidates answer in the spaces provided on the question paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write in dark blue or black pen. 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 all questions. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use: Question Marks 1 2 3 4 5 Total This document consists of 17 printed pages including this page.

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3 [Turn Over No. Experiment Observations Deductions with relevant balanced equations 1. Add ½ spatula of solid potassium carbonate to each separate samples (1 cm 3) of the 4 solutions in clean, dry test tubes. 2. 1 Planning (P) Four aqueous solutions are provided. Each solution contains one of the following: Aluminium bromide, Zinc sulfate, Silver nitrate, Barium hydroxide You are to plan a series of test-t ube experiments using only the four solutions and solid potassium carbonate, in order to deduce which compound is present. No other reagents should be used. You should commence your plan by adding potassium carbonate to each of the solutions. Your completed plan should include observations, deductions and balanced equations for positive tests. [12]

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5 [Turn Over 2 (a) Transition metals are o ften used to p roduce ornamental stained -glass windows. Iron–based colours and pigments have been used since ancient times for stained-glass windows in European churches. (i) Explain why iron compounds are usually coloured. (ii) Explain why the melting point of iron is significantly higher than that of calcium. Stained-glass windows are darkened from corrosion and age. Microprobe analysis showed that the tiny cracks and defects on the glass surface were enriched with insoluble MnO2. (iii) Using the Data Booklet, suggest a suitable redu cing agent to dissolve MnO2 without reducing iron (III) to iron (II). [7]

6 [Turn Over 2 (b) Iron (III) chloride is often used as a catalyst in the conversion of benzene to produce carbonyl compounds. CO / HCl FeCl3 CHO (i) Write an equation to show the generation of the electrophile to form benzaldehyde. (ii) Explain why iron (III) chloride mus t be anhydrous in order to generate the electrophile. [3]

7 [Turn Over 2 (c) By making use of the reaction in 2(b) and suitable starting material