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] (