RI 2019 Prelim P2 QP

1 © Raffles Institution 2019 9729/02/S/19 [Turn Over RAFFLES INSTITUTION 2019 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9729/02 Paper 2 Structured Questions 17 September 2019 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST 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 a 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. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Do not write anything in it. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 8 2 / 7 3 / 16 4 / 9 5 / 15 6 / 20 Total / 75 This document consists of 23 printed pages and 1 blank page.

2 © Raffles Institution 2019 9729/02/S/19 [Turn Over 1 Silicon dioxide is made up of the two most abundant elements on earth, and is the second most abundant mineral. (a) Silicon dioxide is known to occur in as many as 12 different crystalline forms. Unlike SiO2, silicon disulfide, SiS2, lacks such variety in structures. SiS2 reacts quickly with liquid ammonia to form compound X, which has the following composition by mass. Si 48.3%, N 48.1%, H 3.6% Determine the empirical formula of X. [1] (b) Explain the difference in the first ionisation energies of silicon and phosphorus. ……..…………………………………………………………………………………………….. ……………………………………………………………………………………………........... ……………………………………………………………………………………………........... …………………………………………………………………………………………………… …………………………………………………………………………………………………… ………………………………………………………………………………........................ [2] Aluminium and phosphorus are adjacent to silicon in the Periodic Table yet their oxides behave differently as compared to silicon dioxide. (c) Write equations to illustrate the acid -base behaviour of the oxides of aluminium and silicon. ……………………………………………………………………………………………........... ……………………………………………………………………………………………........... ……………………………………………………………………………………………….. [3]

3 © Raffles Institution 2019 9729/02/S/19 [Turn Over (d) Explain, in terms of structure and bonding, why the melting point of P4O10 is lower than that of SiO2. ……………………………………………………………………………………………........... ……………………………………………………………………………………………..