CIE Jun 2015 v5 Paper 3 Q3

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Qualitative Analysis At each stage of any test you are to record details of the following.colour changes seen the formation of any precipitate the solubility of such precipitates in an excess of the reagent added Where gases are released they should be identi ed by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. No additional tests for ions present should be attempted. If any solution is warmed, a boiling tube MUST be used. Rinse and reuse test-tubes and boiling tubes where possible. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given.UCLES 2015 9701/35/M/J/15 [Turn over<br />
 10 (a) FA 1, used in Question 1, is an aqueous solution of sodium thiosulfate. FA 6, used in Question 2, is an aqueous solution of copper(II) sulfate. FA 7 is solid sodium thiosulfate. Carry out the following tests and record your observations in the table below. test observations (i) Using a spatula, place 2 or 3 crystals of FA 7 into a hard-glass test-tube. Heat gently for several seconds, then heat strongly. (ii) To a 1 cm depth of dilute sulfuric acid in a boiling tube, add a few crystals of FA 7. Observe until no further change occurs, then warm the mixture, gently and carefully. (iii) To a 1 cm depth of aqueous potassium iodide in a test-tube, add a few drops of FA 6, aqueous copper(II) sulfate, then add FA 1, aqueous sodium thiosulfate, to the mixture until no further change occurs. (iv) Using your observations in (ii), complete the equation below by giving the formulae of the other two products. Na2S2O3 + H2SO4Na2SO4 + H2O ++[5]UCLES 2015 9701/35/M/J/15<br />
 11 (b) FA 8 and FA 9 are aqueous solutions. Each contains one cation and one anion from those listed on pages 14 and 15. Carry out the tests and record all your observations in the table. For each test, use a 1 cm depth of FA 8 or FA 9 in a test-tube. observations FA 8 FA 9 test (i) Add aqueous sodium hydroxide. (ii) Add a few drops of aqueous silver nitrate followed by aqueous ammonia. (iii) Add aqueous ammonia. (iv) Add an equal depth of dilute sulfuric acid. (v) Add an equal depth of FA 9. (vi) Using your observations, identify three of the ions present in FA 8 and FA 9. Write unknown next to the ion that you cannot identify directly from your observations. ions in FA 8: cationanionions in FA 9: cationanion(vii) The unknown ion in (vi) can be identi ed by elimination, using the lists of ions on pages 14 and 15. Choose one positive test that would con rm the identity of this ion. Name the reagent(s) you would use and state what you would observe if the test was positive. Do not carry out this test. unknown ion tested forreagent(s)observation(s)[8]UCLES 2015 9701/35/M/J/15 [Total: 13]<br />

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