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GCE MAY 2010 : (AS 3) Practical Examination 2 - Revised

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Sp N ec e ifi w ca tio n Centre Number 71 Candidate Number ADVANCED SUBSIDIARy (AS) General Certificate of Education 2010 Chemistry Assessment Unit AS 3 AC132 assessing Module 3: Practical Examination 2 [AC132] TUESDAy 18 MAy, AFTERNOON TIME 2 hours 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all five questions. Write your answers in the spaces provided. INFORMATION FOR CANDIDATES The total mark for this paper is 90. Section A Question 1 is a practical exercise worth 25 marks. Question 2 is a practical exercise worth 29 marks. Section B Question 3 is a planning exercise worth 20 marks. Questions 4 and 5 are written questions worth a total of 16 marks, testing aspects of experimental chemistry. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. Marks Question Number Teacher Examiner Mark Check 1 2 3 4 5 Total Marks 5279 Section A 1 Examiner Only Marks Remark Titration exercise Some liquid drain cleaners contain potassium hydroxide. You are required to carry out a titration and use the results to calculate the concentration of the potassium hydroxide in a liquid drain cleaner. You are provided with: Hydrochloric acid of concentration 0.10 mol dm 3 A solution containing 25.0 cm3 of drain cleaner diluted to 500 cm3 with distilled water Methyl orange indicator (a) Give an account of how you would prepare the diluted solution of drain cleaner and then how you would safely transfer 25.0 cm3 of the diluted solution to a conical flask. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [4] 5279 2 [Turn over (b) Carry out the titration by: Examiner Only Marks Remark rinsing out a burette with the 0.10 mol dm 3 hydrochloric acid filling the burette with the 0.10 mol dm 3 hydrochloric acid transferring 25.0 cm3 of the diluted drain cleaner to the conical flask adding 2 3 drops of methyl orange indicator to the solution in the conical flask and titrating until the end point is reached Present your results in a suitable table and calculate the average titre. [12] (c) State the colour change at the end point of your titration. to 5279 [1] 3 [Turn over (d) Write the equation for the reaction of hydrochloric acid with potassium hydroxide. Examiner Only Marks Remark _____________________________________________________ [1] (e) (i) Calculate the number of moles of hydrochloric acid used in the titration. ___________________________________________________ _________________________________________________ [1] (ii) Calculate the number of moles of potassium hydroxide in 25.0 cm3 of diluted drain cleaner. _________________________________________________ [1] (iii) Calculate the number of moles of potassium hydroxide in 500 cm3 of diluted drain cleaner. _________________________________________________ [1] (iv) Calculate the number of moles of potassium hydroxide in 25.0 cm3 of the undiluted drain cleaner. _________________________________________________ [1] (v) Calculate the concentration of potassium hydroxide in the undiluted drain cleaner in mol dm 3. _________________________________________________ [1] (vi) Calculate the concentration of potassium hydroxide in the undiluted drain cleaner in g dm 3. _________________________________________________ [1] (vii) Assuming the drain cleaner has a density of 1.0 g cm 3 calculate the percentage of potassium hydroxide by mass in the drain cleaner. ___________________________________________________ _________________________________________________ [1] 5279 4 [Turn over BLANK PAGE (Questions continue overleaf) 5279 5 [Turn over 2 Observation/deduction Examiner Only Marks Remark Safety glasses must be worn at all times and care should be taken during this practical examination. (a) You are provided with a mixture of two salts, labelled X, which have a common cation. Carry out the following experiments on the mixture. Record your observations and deductions in the spaces below and identify the two salts. Experiment Observations Deductions 1 Make a solution of X by dissolving half a spatula-measure of X in a test tube half-full of water. Transfer 1 cm3 of this solution into each of two separate test tubes. (a) Add a few drops of sodium hydroxide solution to the first test tube. Then add a further 10 cm3 of the sodium hydroxide solution to the test tube. (b) Add a few drops of dilute ammonia solution to the second test tube. Then add a further 5 cm3 of the ammonia solution to the test tube. 2 Make a solution of X by dissolving half a spatula-measure of X in a test tube half-full of nitric acid solution. Transfer 1 cm3 of this solution into each of two separate test tubes. (a) (i) Add a few drops of silver nitrate solution to the first test tube. (ii) Then add about 5 cm3 of dilute ammonia solution to the same test tube. (b) Add a few drops of barium chloride solution to the second test tube. Name the two salts present in X: _______________________________________________________ _______________________________________________________ 5279 6 [Turn over (b) You are provided with an organic liquid labelled Y. Carry out the following experiments on the liquid. Record your observations and deductions in the spaces below. Experiment Observations Examiner Only Marks Remark Deductions 1 Place 10 drops of Y in a test tube and add 1 cm3 of water. 2 Place 10 drops of Y on a watch glass placed on a heat proof mat and ignite it using a splint. 3 Add approximately 10 drops of Y to a test tube one quarter full of bromine water and mix well. 4 Add 10 drops of Y to 2 cm3 of acidified potassium dichromate solution in a test tube. Warm the mixture gently. Based on the above tests, suggest: a functional group which may be present in Y. _______________________________________________________ a functional group which is absent from Y. ____________________________________________________ [29] 5279 7 [Turn over Section B 3 Examiner Only Marks Remark Planning (a) The empirical formula of an oxide of copper can be found by reducing the copper oxide using the apparatus below. Excess hydrogen burning Hydrogen Copper oxide Heat (i) What weighings should be taken before heating? ___________________________________________________ _________________________________________________ [2] (ii) In addition to wearing safety glasses, suggest and explain one other safety precaution which should be taken. ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (iii) What steps would you take to ensure that all of the oxygen has been removed from the copper? ___________________________________________________ _________________________________________________ [2] (iv) Explain why the hydrogen continues to be passed through the apparatus after all the copper oxide has been reduced. ___________________________________________________ _________________________________________________ [2] 5279 8 [Turn over (b) When 2.16 g of the copper oxide was reduced, 1.92 g of copper was formed. Examiner Only Marks Remark (i) What mass of oxygen was present in the copper oxide? _________________________________________________ [1] (ii) How many moles of oxygen were present in the copper oxide? _________________________________________________ [1] (iii) How many moles of copper were formed? _________________________________________________ [1] (iv) Calculate the empirical formula of the copper oxide. ___________________________________________________ _________________________________________________ [2] 5279 9 [Turn over (c) Copper can be extracted from its ore, chalcopyrite, CuFeS2. Examiner Only Marks Remark The chalcopyrite is converted to copper(I) sulphide, Cu2S. Some of the copper(I) sulphide is converted to copper(I) oxide, Cu2O, and sulphur dioxide by heating in air. The copper(I) oxide then reacts with the remaining copper(I) sulphide to form copper and sulphur dioxide. (i) Write the equation for the formation of the copper(I) oxide and sulphur dioxide. _________________________________________________ [2] (ii) Write the equation for the formation of the copper. _________________________________________________ [1] (iii) A sample of chalcopyrite weighing 25.86 g contains 34.8% by mass of CuFeS2. Calculate the percentage of copper in the sample of chalcopyrite using the following headings. Mass of CuFeS2 in the sample ___________________________________________________ Percentage of copper in CuFeS2 ___________________________________________________ Mass of copper in the sample ___________________________________________________ Percentage of copper in the sample _________________________________________________ [4] 5279 10 [Turn over 4 2-bromobutane (boiling point 91 C) can be prepared by firstly mixing sodium bromide, butan-2-oI and water in a pear-shaped flask. Concentrated sulphuric acid is then added slowly and the mixture gently refluxed. Examiner Only Marks Remark (a) Explain what is meant by refluxed. _____________________________________________________ [1] (b) After refluxing, the mixture is distilled and an impure sample of the 2-bromobutane collected. (i) Describe how acid impurities could be removed from the impure sample. ___________________________________________________ _________________________________________________ [2] (ii) Describe how any trace of water could be removed from the impure sample. ___________________________________________________ _________________________________________________ [2] (iii) Describe how a pure sample of the 2-bromobutane could be obtained from the remaining liquid. ___________________________________________________ _________________________________________________ [2] 5279 11 [Turn over 5 A white solid is thought to be either potassium chloride or potassium iodide. Examiner Only Marks Remark (a) Describe how you would carry out a flame test to show the presence of potassium ions in the white solid. State the flame colour expected. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [3] (b) Describe how you would confirm the presence of chloride or iodide ions using dilute nitric acid and silver nitrate solution. State any observations expected. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [3] (c) Describe how silver chloride and silver iodide react with dilute and with concentrated ammonia solutions. State any observations expected. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [3] THIS IS THE END OF THE QUESTION PAPER 5279 5279 12 [Turn over Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. 1847-071-1

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Additional Info : Gce Chemistry May 2010 Assessment Unit AS 3 Module 3: Practical Examination 2 - Revised
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