IJC_H1_CHEM_P2

INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2 in preparation for General Certificate of Education Advanced Level Higher 1 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Structured and Free Response Questions Section A: Structured Candidates answer Section A on the Question Paper Section B: Free Response Additional Materials: Writing Papers Data Booklet 8872/02 24 September 2009 2 hours READ THESE INSTRUCTIONS FIRST Write your index number, name and civics group on all the work you hand in. Write in dark blue or black pen. You may use pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A: Structured Questions (40m) Answer all questions in the space provided. For Examiner’s Use Section A 1 10 2 10 3 9 4 11 Significant Figures Total 40 Section B: Free Response Questions (40m) Answer two questions on separate writing papers. You are advised to show all working in calculations. You are reminded of the need for good English and clear presentation in your answers. You are reminded of the need for good handwriting. Your final answers should be in 3 significant figures. You may use a calculator. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. This document consists of 17 printed pages and 1 blank page. Innova Junior College [Turn over

PRELIM 2  INNOVA 8872/02/09 [Turn over 2 For Examiner’s Use Section A Answer ALL questions on the space provided. 1 The purity of iodates ( VII) can be estimated by adding an acidified solution of potassium iodide and titrating the iodine produced with aqueous sodium thiosulphate. In one such analysis, a 0.100 g sample of impure sodium iodate ( VII), Na 5IO6, was dissolved in water and treated with an excess of acidified KI. IO6 5- + 7I- + 12H+ 4I2 + 6H2O The iodine liberated required 22.0 cm 3 of 0.100 moldm-3 sodium thiosulphate, Na 2S2O3 to reach its end point. Calculate the purity of the sodium iodate (VII). (a) (i) Write a balanced ionic equation for the reaction between thiosulphate and iodine. (ii) Calculate the number of moles of iodine liberated. (iii) Calculate the number of moles of pure Na 5IO6 required to produce the iodine in part (ii). (iv) Calculate the mass of pure Na 5IO6 in the sample. (v) Calculate the purity of the sodium iodate (VII).