RVHS Prelim P4 Soln

River Valley High School Pg 1 JC 2 H2 Chemistry 9729 2021 Prelim Practical Examination RIVER VALLEY HIGH SCHOOL JC 2 PRELIM PRACTICAL EXAMINATION H2 CHEMISTRY 9729 Paper 4 19 AUGUST 2021 2 HOURS 30 MINUTES NAME CLASS 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 total 55 _________________________________________________________________________________ This Question Paper consists of 20 printed pages and 1 blank page. Answer all the questions in the spaces provided.

River Valley High School Pg 2 JC 2 H2 Chemistry 9729 2021 Prelim Practical Examination 1 Determine the solubility product, Ksp, of calcium iodate(V), Ca(IO3)2 For Examiner’s Use Calcium iodate is used in the manufacture of disinfectants, antiseptics, and deodorants. Its solubility in water is low. When calcium iodate(V) is mixed with water, the following equilibrium is established. Ca(IO3)2(s) = Ca2+(aq) + 2IO3-(aq) The total amount of IO3-(aq) in the saturated salt solution is determined using iodometry. Excess potassium iodide, KI, is added to an acidified solution of the filtrate, liberating iodine. Reaction 1 IO3-(aq) + 5I-(aq) + 6H+(aq) ® 3I2(aq) + 3H2O(l) The liberated iodine is then titrated with a standard solution of sodium thiosulfate. Reaction 2 2S2O32-(aq) + I2(aq) ® 2I-(aq) + S4O62-(aq) (a) You are provided with FA 1 a saturated solution of Ca(IO3)2 in KIO3(aq) FA 2 0.200 mol dm-3 sodium thiosulfate, Na2S2O3 FA 3 aqueous solution of potassium iodide, KI FA 4 dilute sulfuric acid, H2SO4 Starch indicator Titration of filtrate, FA 1 1. Pipette 25.0 cm3 of FA 1 into a conical flask. 2. Using a measuring cylinder, add about 10 cm3 of FA 4 to the conical flask. 3. Using another measuring cylinder, add about 10 cm3 of FA 3 to the conical flask. 4. Add FA 2 from the burette into the conical flask until a pale yellow solution is obtained. 5. Add about 5 drops of starch indicator and continue adding FA 2 until the blue-black colour just disappears. 6. Record your titration results, to an appropriate level of precision, in the space on Page 3. 7. Repeat the titration as many times as necessary until consistent results are obtained.

River Valley High School Pg 3 JC 2 H2 Chemistry 9729 2021 Prelim Practical Examination Results Titra