RVHS Prelim P4 QP

River Valley High School Pg 1 of 24 JC 2 H2 Chemistry 9729 2020 Prelim Practical Examination RIVER VALLEY HIGH SCHOOL JC 2 PRELIM PRACTICAL EXAMINATION H2 CHEMISTRY 9729 Paper 4 25 AUGUST 2020 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 s.f. / d.p. units total 55 _________________________________________________________________________________ This Question Paper consists of 23 printed pages and 1 blank page.

River Valley High School Pg 2 of 24 JC 2 H2 Chemistry 9729 2020 Prelim Practical Examination Answer all the questions in the space provided. 1 Determination of a value for the solubility product, Ksp, of calcium iodate(V), Ca(IO3)2 For Examiner’s Use Calcium iodate (V), Ca(IO3)2, is a colourless salt that occurs naturally as the mineral, lautarite. It is used in the manufacture of disinfectants, antiseptics, deodorants and as iodine supplement in chicken feed. Ca(IO3)2 has low solubility in water. When a sample of this salt is mixed with water, the following equilibrium is established. Ca(IO3)2(s)  Ca2+(aq) + 2IO3(aq) You are to perform an experiment to determine the solubility product, Ksp, of Ca(IO3)2(s). Ca(IO3)2(s) is added to a specific volume of aqueous potassium iodate(V), KIO3, with known concentration. The mixture is then filtered after leaving to stand for some time. The total amount of IO3(aq) is determined as described below. Excess potassium iodide, K I, 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) Write an expression for the solubility product, Ksp, of calcium iodate(V). 1 (b) The following procedure is used to prepare a saturated solution of calcium iodate(V) in aqueous potassium iodate(V), FA 1. You do not need to perform this part of the experiment. 1. Using a measuring cylinder, transfer 100.0 cm3 of 0.0100 mol dm3 KIO3 to a clean, dry beaker. 2. Add 2 spatulas of solid Ca(IO3)2 to the same beaker. 3. Stir the mixture thoroughly. There should be u