RJC_Chemistry H1 P2 with Ans Prelims

©RJC 2008 [Turn over 1 RAFFLES JUNIOR COLLEGE PRELIMINARY EXAMINATION 2008 Higher 1 CANDIDATE NAME C L A S S I N D E X N U M B E R CHEMISTRY 8872/02 Paper 2 15 September 2008 2 hours Candidates answer Section A on the Question Paper. Additional Materials: Answer Paper Data Booklet READ THESE INSTRUCTIONS FIRST DO NOT open this question booklet until you are told to do so. Write your name, class and index number in the spaces provided on the cover page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer two questions on separate answer paper. A Data Booklet is provided. Do not write anything on it. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A /40 B6 /20 B7 /20 B8 /20 Total /80 This question booklet consists of 12 printed pages.

©RJC 2008 [Turn over 2 Section A Answer all questions in this section in the spaces provided. 1 (a) To determine the concentration of lead( II) ions in a sample of lead( II) nitrate solution, 25.0 cm 3 of the solution was added to 40.00 cm 3 of 0.400 mol dm −3 hydrochloric acid. Lead( II) chloride was precipitated out and the mixture was filtered. It was found that 25.0 cm 3 of the filtrate required 27.45 cm 3 of 0.150 mol dm −3 silver nitrate solution for complete reaction. Calculat e the concentration of lead( II) ions in the lead(II) nitrate solution. [4] (b) Sodium nitrite, NaNO 2, is used as a preservative in meat products such as frankfurters and bologn a. In an acidic solu tion, nitrite ion, NO 2 −, is oxidised to nitrate ion, NO 3 −, when it reacts wit h the manganate(VII) ion, MnO4 −. A 1.00 g sample of a water-soluble solid containing NaNO2 was dissolved in dilute H 2SO4 and titrated with 0.0100 mol dm −3 aqueous KMnO 4 solution. The titration required 12.15 cm 3 of the KMnO4 solution. (i) Write an equation for the reaction between MnO 4 − and NO2 −.

©RJC 2008 [Turn over 3 (ii) Calculate the percentage by mass of NaNO 2 in the 1.00 g sample. [4] [Total: 8] 2 (a) The identities of three unknown elements X, Y and Z are rubidium (Rb), strontium (Sr) and caesium (Cs) but not necessarily in that order. The order of the elements in order of increasing first ionisation energy is X < Y < Z. (i) Suggest the ident ity of each element X, Y and Z