PJC H2 Chem 2013 Prelim P2 Soln

1 © PJC 2013 9647/02/JC2 Prelim/2013 PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION HIGHER 2 CANDIDATE NAME CT INDEX GROUP NUMBER CHEMISTRY 9647/02 Paper 2 Structured 18 September 2013 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name on all work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough workings. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 20 printed pages. FOR EXAMINER’S USE Paper 2 1 / 12 5 / 5 2 / 10 6 / 7 3 / 14 Penalty sf units 4 / 24 Total / 72 Suggested Answers 1 2 983

2 © PJC 2013 9647/02/JC2 Prelim/2013 1 Planning Heat is absorbed when potassi um iodide dissolves in water. Sucrose, on the other hand, does not produce a temperature change when added to water. By studying the temperature changes wh en known masses of potassium iodide dissolve, the percentage by mass of potassi um iodide in a mixture of potassium iodide and sucrose, FA 5 can be determined. You are provided with  a test tube of FA 1 which contains 2.00 g of potassium iodide  a test tube of FA 2 which contains 4.00 g of potassium iodide  a test tube of FA 3 which contains 6.00 g of potassium iodide  a test tube of FA 4 which contains 8.00 g of potassium iodide  an empty test tube labelled FA 5  FA 5, a mixture of potassium iodide and sucrose  a thermometer  a polystyrene cup  other common apparatus in the laboratory (a) The percentage composition of potassium iodide in the mixture, FA5, is estimated to be 50%. Suggest a suitable value for mass of FA 5 used. 4.00 < mass of FA 5 (x) < 16.00 [1] (b) Describe, in a series of numbered steps, how you would measure the temperature changes by dissolving separate samples of FA 1 to FA 5 in water. Hence, determine the mass of potassium iodide in a mixture of FA 5. Your plan should include the following:  the apparatus for measurements  how you would take and record the various measurements  the tables for record ing the data measured  the graph to be plotted 1. Using a wei ghing balance, weigh out accurately x g of FA 5 in a test tube labelled FA 5. Record the mass in the table below. Mass of test tube + FA 5 / g Mass of empty test tube / g Mass of FA 5 used / g x 2. Measure 50 cm 3 of deionised water using