RVHS Prelim P4_Soln

River Valley High School Pg 1 of 20 Year 6 H2 Chemistry 9729 Practical Examination 2018 RIVER VALLEY HIGH SCHOOL YEAR 6 PRACTICAL EXAMINATION II H2 CHEMISTRY 9729 23 AUGUST 2018 2 HOURS 30 MINUTES NAME CLASS 6 ( ) INDEX NO. INSTRUCTIONS TO CANDIDATES DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Read these notes carefully. Write your name, class and index number in the spaces at the top of this page. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a 2B pencil for any diagrams or graph. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Shift Laboratory For Examiner’s Use 3 s.f. Units Total 55 _________________________________________________________________________ This Question Paper consists of 14 printed pages and 1 blank page. Answer all the questions in the spaces provided.

River Valley High School Pg 2 of 20 Year 6 H2 Chemistry 9729 Practical Examination 2018 1 To investigate the kinetics of the reaction between iron( III) ions and iodide ions For Examiner’s Use You will investigate rate of oxidation of iodide by iron( III) ions in reaction 2 . The chemical changes in this experiment can be presented by the following equations: Reaction 1: Fe3+(aq) + S2O32–(aq) ⇌ [Fe(S2O3)]+(aq) Reaction 2: 2Fe3+(aq) + 2I–(aq) → 2Fe2+(aq) + I2(aq) Reaction 3: I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O62–(aq) The reaction is started by mixing acidic solution of iron(III) chloride with sodium thiosulfate, potassium iodide, and starch. The iodine, I2, produced in reaction 2 reacts immediately with thiosulfate ions, S2O32– in reaction 3. When all the thiosulfate has been used, the iodine produced will turn starch indicator blue-black. The rate of the reaction can therefore be determined by finding the time for the blue-black colour to appear. FA 1 is 0.030 mol dm –3 iron(III) chloride, FeCl3. FA 2 is 0.060 mol dm–3 potassium iodide, KI. FA 3 is 0.0060 mol dm–3 sodium thiosulfate, Na2S2O3. starch indicator You are advised to read the instructions before starting any practical work and draw a table, in an appropriate format, for your results in the space on page 4. You will need to include volume of FA 1, volume of water, reaction time and calculated rate of reaction for each of the five experiments. Record all calculated values to 3 significant figures. (a) Method Experiment 1 1. Use the measuring cylinders to place the following in a 100 cm 3 beaker. • 10 cm 3 of FA 2 • 20 cm 3 of FA 3 • 10 cm 3 of starch indicator 2. Using a measuring cylinder, transfer 20 cm 3 of FA 1 rapidly into t