IJC H2 CHEM P2 students copy

INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION in preparation for General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper Additional Materials: Data Booklet 9647/02 18 August 2016 2 hours READ THESE INSTRUCTIONS FIRST Write your index number, name and civics group. Write in dark blue or black pen. You may use pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the space provided. A Data Booklet is provided. You are advised to show all working in calculations. You are reminded of the need for good English and clear presentation in your answers. You are reminded of the need for good handwriting. Your final answers should be in 3 significant figures. You may use a calculator. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. This document consists of 17 printed pages and 1 blank page. Innova Junior College [Turn over For Examiner’s Use Section A 1 12 2 17 3 10 4 18 5 15 Significant figures Handwriting Total 72

2  IJC 2016 Prelim/9647/02 [Turn over For Examiner’s Use Answer ALL questions on the spaces provided. 1 Planning Using the information below, you are to write a plan for determining number of molecules of water of crystalisation, n, in barium chloride crystals, BaC l2.nH2O where n = 1,2 or 3. The basis of this investigation is a technique known as precipitation titration with the use of silver nitrate solution, AgNO3(aq). AgCl, Ag2CrO4 and BaCrO4 are sparing soluble salts and relevant information about these salts are given in the table below. compound colour numerical value of Ksp at 25 O C AgCl white 2.0 × 10−10 Ag2CrO4 red 2.0 × 10−12 BaCrO4 yellow 1.0 × 10−10 Some barium chloride crystals, BaCl2.nH2O, is dissolved to make up 250.0 cm3 of standard solution. Approximately 10 cm 3 of 0.2 mol dm −3 of reagent X solution is added to a portion of this standard solution to precipitate the barium ions before a few drops of K 2CrO4 indicator solution is added. A titration is then carried out on this portion of solution against silver nitrate solution, AgNO 3(aq). Ag 2CrO4 would just precipitate only when almost all of the Cl− ions have been precipitated as AgC l. The titration is repeated until a more reliable average value, V cm3, can be determined. (a) (i) Identify reagent X. ……...……………………………………………………………………………… [1] (ii) A student suggested that BaCrO4 is more soluble than Ag2CrO4 as BaCrO4 has larger numerical value of Ksp than Ag2CrO4. Suggest whether this student’s claim is valid. ……………………………………………………………………………………........ ……………………………………………………………………………………........ ……………………………………………………………………………………........ ……………………………………………………………………………………........ ……...……………………………………………………………………………… [1] (iii) Suggest why reagent X is added before a few drops of K2CrO4 indicator solution is added. ……………………………………………………………………………………........ ……………………………………………………………………………………........ ……...……………………………………………………………………………… [1]

3  IJC 2016 Prelim/9647/02 [Turn over For Examiner’s Use (b) You may assume that you are provided with  0.10 mol dm−3 silver nitrate  0.2 mol dm−3 of reagent X solution  10 g of barium chloride crystals, BaCl2.nH2O  Potassium chromate solution, K2CrO4(aq)  The equipment and mater ials normally found in a school or college laboratory. Your plan should include the following  brief, but specific details of the apparatus you would use, bearing in mind the levels of precision they offer  details, including quantities, for preparat ion of 250.0 cm 3 of BaCl2 solution from barium chloride crystals, BaCl2.nH2O  essential details of the titration procedure  an outline of how the results obtained, including V cm3, would be used to determine n, in barium chloride crystals (BaCl2.nH2O) …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... ……...……………………………………………………………………………………......… …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......…

4  IJC 2016 Prelim/9647/02 [Turn over For Examiner’s Use ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... …………………………………………………………………………………….................... ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......…

5  IJC 2016 Prelim/9647/02 [Turn over For Examiner’s Use ……...……………………………………………………………………………………..... [8] (c) Explain why this titration cannot be conducted under acidic or alkaline medium. ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………......… ……...……………………………………………………………………………………..... [1] [Total: 12]

6  IJC 2016 Prelim/9647/02 [Turn over For Examiner’s Use 2 This question is about the oxides of nitrogen and its reactions. Oxides of nitrogen constitute air pollutants originating from emission of car exhaust that cause acid rain and photochemical smog. The two gases of NO and N2O4 slowly react t