CJC Prelim P3

9729/03/CJC JC2 Preliminary Examination 2018 CANDIDATE NAME CLASS 2T CHEMISTRY 9729/03 Paper 3 Free Response Friday 24 August 2018 2 hours Candidates answer on separate paper. Additional Materials: Answer 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. 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 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 examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 10 printed pages. Catholic Junior College JC2 Preliminary Examinations Higher 2

2 9729/03/CJC JC2 Preliminary Examination 2018 Section A Answer all the questions in this section. 1 Propene is a colourless gas that is produced in large quantities by the petrochemical industry. It is used in the production of synthetic rubber and as a propellant in aerosols. (a) When propene reacts with HBr, 2-bromopropane is produced as the major product. CH2=CHCH3 + HBr → CH3CHBrCH3 (i) Describe the mechanism of the above reaction, using curly arrows to show the movement of electrons. [4] (ii) When propene reacts with BrC l, 1-bromo-2-chloropropane is produced as the major product. CH 2=CHCH3 + BrCl → CH2BrCHClCH3 With reference to your answer in (i), explain why the two reactions give major products with bromine in different positions. [2] (iii) The product of the reaction in (ii) has a chiral carbon, but it is optically inactive. Explain why this is so. [2] (b) 2-bromopropane reacts with hot aqueous sodium hydroxide, whereas 2-bromopropene does not. Suggest reasons for this difference in reactivity. [2] (c) Propene can undergo mild oxidation in the presence of cold acidified potassium manganate(VII), to give CH 2(OH)CH(OH)CH3. (i) State the IUPAC name of the product of the above reaction. [1] (ii) Construct the half ‒equation for the oxidation of propene as described above. [1] (iii) Hence, write the equation for the overall reaction, showing clearly the stoichiometry of reaction between propene and manganate(VII) ions. [1] (d) At room temperature and pressure, 28 cm 3 of propene was bubbled into 40.0 cm3 of 0.0200 mol dm‒3 acidified KMnO4(aq). The resulting solution was titrated against Fe2+(aq) of concentration 0.0750 mol dm‒3. (i) State the colour change at endpoint for this titration. [1] (ii) Given that 5 moles of Fe 2+ react with 1 mole of MnO4 ‒, determine the volume of Fe2+(aq) needed to reach endpoint. [3] (e) A mixture of propene (