RI Prelim P3 (Qns)

© Raffles Institution 2020 9729/03/S/20 [Turn Over RAFFLES INSTITUTION 2020 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9729/03 Paper 3 Free Response 18 September 2020 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 t he 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 / 19 (Circle the question you have answered) / 80 2 / 20 4 / 20 3 / 21 5 / 20 This document consists of 35 printed pages.

2 © Raffles Institution 2020 9729/03/S/20 For examiner’s use Section A Answer all the questions in this section. 1 In an aerosol spray , liquefied -gas propellants are sealed in a pressurised canister. Upon release into the air, the propellants instantly vaporise. Table 1.1 shows the boiling points of some aerosol propellants. Table 1.1 propellant CF2Cl2 N2O CH3OCH3 boiling point / oC −30 −89 −24 Mr 121.0 44.0 46.0 (a) (i) In N2O, the central atom is nitrogen. Draw a dot-and-cross diagram to show the bonding in N2O. Include all lone pairs in your diagram. [1] (ii) Predict and explain the shape and bond angle about the oxygen atom in CH3OCH3. [2] (iii) Explain why CH3OCH3 has a higher boiling point than CF2Cl2. [1] ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..…..............