RI 2021 Prelim P3 QP

RAFFLES INSTITUTION 2021 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9729/03 Paper 3 Free Response 17 September 2021 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write your name, class and index number in the spaces provided at the top of this page. 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. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Do not write anything in it. You are reminded of the need for good English and clear presentation in your answers. 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 Section A Section B Total 1 / 23 (Circle the question you have answered) / 80 2 / 20 4 / 20 3 / 17 5 / 20 This document consists of 32 printed pages and 4 blank pages.

2 © Raffles Institution 2021 9729/03/S/21 [Turn Over Section A Answer all the questions in this section. 1 Alcohols, carbonyl compounds and esters are commonly found in both natural and artificial flavourings. (a) (i) When iodine dissolves in hexane, the solution is purple. Describe a reaction that uses this observation to illustrate the relative oxidising abilities of iodine and chlorine. [1] (ii) Explain the above reaction using relevant E ⦵ values from the Data Booklet. [1] (iii) Ascorbic acid (Mr = 176.0) is a food additive commonly added to candy to give a sour flavour. Iodine can be used to determine the amount of ascorbic acid in food by oxidising the ascorbic acid to dehydroascorbic acid. A 100.0 g sample of a candy w as dissolved in hot water. The resulting solution was filtered and diluted to 100 cm3 in a volumetric flask. A 10.0 cm3 aliquot of the solution was pipetted into a conical flask and a few drops of starch solution was added. The sample was then titrated w ith 0.005 mol dm–3 of iodine solution. The titre volume was 22.05 cm3. Calculate the percentage by mass of ascorbic acid in the candy. [3] …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ……………………………………………………………………………………...

3 © Raffles Institution 2021 9729/03/S/21 [Turn Over …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. (b) Alcohols can be prepared from halogenoalkanes. Three different halogenoalkanes, bromopropane, chloropropane and iodopropane, were hydrolysed to form propanol. Outline how you would determine the difference in the rate of hydrolysis of the three compounds. You should include the expected observations of the experiment. You are provided with 0.10 mol dm–3 silver nitrate solution in ethanol and the pure halogenoalkanes in liquid state. Details regarding use of specific glassware are not required. [3] ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........ ……………………………………………………………………………………..…........

4 © Raffles Institution 2021 9729/03/S/21 [Turn Over (c) The characteristic berry flavour found in red raspberries is due to the phenolic compound known as raspberry ketone (RK). raspberry ketone (RK) (i) Draw the structure of the organic product formed when RK is reacted with an excess of Br2(aq). [1] (ii) RK can be converted to rhododendrol. rhododendrol State the reagent s and conditions required to convert RK to rhododendrol and name the type of reaction which occurred. [1] (iii) By comparing the relative acidities of the relevant functional groups, explain the reaction when sodium hydroxide is added to rhododendrol. [2] (iv) Describe a chemical test, with appropriate observations, which would distinguish between RK and rhododendrol. [2] …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. ……………………………………………………………………………………..

5 © Raffles Institution 2021 9729/03/S/21 [Turn Over …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ……………………………………………………………………………………..

6 © Raffles Institution 2021 9729/03/S/21 [Turn Over (d) Another additive commonly used in perfumes is gardenol which imparts a floral scent. When gardenol, C 10H12O2, is heated with dilute H2SO4, two compounds B and C are formed. Compound B liberates CO2 from Na2CO3. (i) Name the type of reaction shown and suggest the functional groups present in gardenol, B and C. [2] When heated with acidified KMnO 4, gardenol forms compounds B and D. Compound C also forms compound D when heated with acidified KMnO 4. Compound C contains a chiral centre, while compound B does not. (ii) Deduce the structures of compounds B, C, D and gardenol, explaining the reactions described. [5] (iii) Based on your structure of compound C, explain which carbon is chiral, and draw the pair of enantiomers. [2] …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………………. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ……………………………………………………………………………………….