MI H2 Chem 2012 Prelim P3 QP

Class Adm No Candidate Name: 2012 Preliminary Examination II Pre-university 3 H2 CHEMISTRY 9647/03 Paper 3 14 Sept 2012 2 hours Additional Materials: Writing Paper Data Booklet Graph Paper READ THESE INSTRUCTIONS FIRST 1. Do not turn over this question paper until you are told to do so. 2. Write your name, class and index number in the spaces provided at the top of this page and on all the work you hand in. 3. Write in dark blue or black pen on both sides of the paper. 4. You may use a soft pencil for any diagrams or graphs. 5. DO NOT use staples, paper clips, highlighters, glue or correction fluid or tape. 6. Answer any four questions. 7. Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place in the case of Mr and Ar, unless a different level of accuracy is specified in the question. 8. The number of marks is given in brackets [ ] at the end of each question or part question. 9. You are reminded of the need for good English and clear presentation in your answers and to show all working in calculations. 10. The use of a calculator is expected, where appropriate. This question paper consists of 7 printed pages. [Turn over

- 2 - Answer ANY FOUR quest ions 1 (a) When studying Hydrocarbons, we recognised the environmental consequences of carbon monoxide, oxides of nitrogen and unburnt hydrocarbons arising from the internal combustion engine. Because of these environmental concerns, alongside with high oil prices and oil being a limited natural resource, development of cleaner alternative fuels and advanced power systems for vehicles has become a high priority for many governments and vehicle manufacturers around the world. An alternative fuel vehicle is a vehicle that runs on a fuel other than "traditional" petroleum fuels (petrol or diesel); and also refers to any technology of powering an engine that does not involve solely petroleum (e.g. electric car, hybrid electric vehicles, solar powered). One such source of alternative fuel is the hydrogen / oxygen fuel cell , which is increasingly used in space crafts. Describe, providing details, the hydrogen / oxygen fuel cell. Include the following in your answer: · Draw a well-labeled diagram for the cell. · Outline the reactions taking place at each electrode, assuming an alkaline medium. · State one advantage of using this fuel cell. [6] (b) C yanogen is a highly toxic gas, composing of 46.2% carbon and 53.8% nitrogen by mass. At 25 ºC and 1 atm, 1.05 g of cyanogen occupies 0.500 dm3. (i) Determine the molecular formula of cyanogen. (ii) Draw the dot-and-cross diagram for cyanogen. Hence, state its shape. (iii) ‘Cyanogen is soluble in ethanol.’ Explain this statement with the aid of a suitable diagram. [7] (c) S ketch and explain the trend observed for the atomic and ionic radii of the elements (from Na to Cl) in Period 3. [4] (d) P hosphine, PH3, a gas at room temperature can be prepared by action of sodium hydroxide on phosphonium