HCI_H2_CHEM_P2 Prelim

This document consists of 17 printed pages and 1 blank page. HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 10S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 2 Structured Additional Materials: Data Booklet 9647/02 21 September 2011 2 hours INSTRUCTIONS TO CANDIDATES 1) Write your name , CT group, centre number and index number clearly in the spaces at the top of this page. 2) Answer all questions in the spaces provided in this Question Booklet. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. A Data Booklet is provided . Do not use staples, paper clips, highlighters, glue or correction fluid. You may use a calculator. You are reminded of the need for good English and clear presentation in your answers. For Examiner’s Use 1 / 12 2 / 23 3 / 16 4 / 9 5 / 12 Total / 72

2 © Hwa Chong Institution 2011 9647 / 02 / JC2 Prelim 2011 1 Planning (P) Ammonium salts are commonly used in instant cold p acks. The cold pack contains water, and in the water is another pouch containing the ammoni um salt. When the pack is squeezed, this inner pouch is broken, releasing the salt, which qu ickly dissolves and lowers the pack’s temperature. To determine whether ammonium chloride or ammonium nitrate is more effective as the ingredient in the cold pack, a student decided to c onduct an experiment to find out the enthalpy change of solution of the two salts, starting with ammonium chloride. He added ammonium chloride to water and found the t emperature change by plotting a suitable graph to correct for surrounding heat transfer. Solubility of ammonium chloride at 25 oC = 6.95 mol dm –3 4.3 J are required to raise the temperature of 1.0 cm 3 of any solution by 1° C. In a preliminary investigation, the enthalpy change of solution of ammonium chloride was found to be approximately +15 kJ mol –1 . (a) Draw a labelled diagram to show the apparatus you could use in a school laboratory to carry out the experiment. [1] (b) (i) By considering the apparatus chosen in your diagra m, state a volume of water you could use in the experiment. Volume of water = ……………………………………………….. cm 3

3 © Hwa Chong Institution 2011 9647 / 02 / JC2 Prelim 2011 (ii) Calculate the maximum mass of ammonium chloride th at can be added to the volume of water stated in (b)(i) . [2] (c) Suggest a minimum mass of ammonium chloride that c ould be used. Justify your choice with relevant calculations, stating any assumptions you made. [2] (d) Describe the procedure to find the enthalpy change of solution of ammonium chloride. In your plan,