DHS H2 Chem 2013 Prelim P2 QP

__________________________________________________________________________________ This question paper consists of 18 printed pages and 0 blank page. © DHS 2013 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H2 CHEMISTRY 9647/02 Paper 2 Structured 19 September 2013 2 hours Additional Materials: Data Booklet INSTRUCTIONS TO CANDIDATES 1 Write your name, index number and class on this cover page. 2 Answer all questions. 3 Write your answers in the spaces provided on the question paper. 4 A Data Booklet is provided. 5 The number of marks is given in brackets [ ] at the end of each question or part question. 6 You may use a calculator. For Examiner’s Use 1 / 12 2 / 15 3 / 9 4 / 10 5 / 15 6 / 11 Total / [72] % 492

2 © DHS 2013 9647/02 [Turn over Answer all questions in the space provided. 1 Planning Solubility is defined as the mass of solid that will dissolve in and just saturate 100 g of solvent at a particular temperature. When potassium nitrate dissolves in water, the temperature of the solution decreases as the enthalpy change of solution is endothermic. You are to plan an experiment to investigate how the solubility of potassium nitrate varies with temperature. The units of solubility are grams per one hundred grams of water (g/100 g of water). (a) (i) Predict how the solubility of potassium nitrate will change if the solution temperature is increased. (ii) Display your prediction in the form of a sketch, labeling clearly the y–axis. 25 temperature / °C [3] For  Examiner’s  Use 493

3 © DHS 2013 9647/02 [Turn over (b) You are to design an experiment to test your prediction in (a). (i) Given that the solubility of potassium nitrate at 70 °C = 11.3 mol dm–3 Calculate the maximum mass of potassium nitrate that can be dissolved in 100 g of water at 70 °C. (ii) Describe how you would carry out the experiment. You should • include the apparatus used; • ensure a wide range of results suitable for analysis by graph; • decide on the amount of water and potassium nitrate to be used; and • describe how the temperature of the solution is to be maintained. You may also assume that standard laboratory apparatus are available. For  Examiner’s  Use  494

4 © DHS 2013 9647/02 [Turn over (iii) Draw a table with appropriate headings to show the data you would record when carrying out your experiments and the values you would calculate in order to construct a graph to support or reject your prediction in (a). The headings must include the appropriate units.