SJI_2020 Year 3 EOY Chemistry 6092 P2

1 ST JOSEPH’S INSTITUTION END-OF-YEAR EXAMINATION 2020 (YEAR 3) CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Additional Materials: NIL 6092 / 02 1 OCTOBER 2020 1 hour 40 minutes (0800 - 0940) READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black ink pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided. Section B Answer all questions in the spaces provided. 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. The use of an approved scientific calculator is expected, where appropriate. A copy of the Periodic Table is printed on page 2. For Examiner’s Use Section A / 40 Section B / 30 Total / 70 This document consists of 21 printed pages including this cover page.

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3 Section A Answer ALL questions in the spaces provided. The total mark for this section is 40. A1 An ester is a substance formed between the reaction of two organic compounds, an alcohol and an organic acid. An example of an ester is propyl ethanoate formed by the reaction of propanol (alcohol, C3H7OH, boiling point 97 °C) and ethanoic acid (organic acid, CH3COOH, boiling point 120 °C) with a small amount of concentrated sulfuric acid as a catalyst. (a) The glassware, as shown in Figure 1.1 and Figure 1.2 below, can be used for the formation of an ester, both using the same quantities of chemicals from the start. Figure 1.1 Figure 1.2 (i) Suggest a reason for using a water bath instead of direct heating. …………………....….……………………………………………………………. ………..…………………………………………………..…………………….[1] HEAT water bath test tube Liebig condenser Mixture of propanol, ethanoic acid and concentrated acid water bath HEAT

4 (ii) After heating the reaction mixture for a while, a student discovered that the percentage yield of ester from the set up in Figure 1.2 is less than that from the set up in Figure 1.1. Explain why. ………….….……………………………...………………………………………. ………….….…………………………………...…………………………………. ………….….………………………………...……………………………………. ………..……………………………………..………………………………….[2] (b) Esters can be used as solvents in chromatography. The following shows a chromatogram of plant acids which is drawn to scale. An ester was used as the solvent and the chromatogram was sprayed with a locating agent, bromothymol blue. sample 1 sample 2

5 (i) Suggest why it was necessary to spray the chromatogram