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GCE MAY 2010 : (AS 3) Practical Examination 1 - 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 AC131 assessing Module 3: Practical Examination 1 [AC131] FRIDAy 14 MAy, MORNING TIME 2 hour 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 Marks Check 1 2 3 4 5 Total Marks 5278 Section A 1 Examiner Only Marks Remark Titration Exercise Some liquid oven cleaners contain sodium hydroxide. You are required to carry out a titration and use the results to calculate the concentration of the sodium hydroxide in a liquid oven cleaner. You are provided with: Hydrochloric acid of concentration 0.10 mol dm 3 A solution containing 25.0 cm3 of oven cleaner diluted to 500 cm3 with distilled water Methyl orange indicator (a) Give an account of how you would prepare the diluted solution of oven cleaner and then how you would safely transfer 25.0 cm3 of the diluted solution to a conical flask. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [4] 5278 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 oven 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 ________________________ 5278 3 [1] [Turn over (d) Write the equation for the reaction of hydrochloric acid with sodium 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 sodium hydroxide in 25.0 cm3 of the diluted oven cleaner. _________________________________________________ [1] (iii) Calculate the number of moles of sodium hydroxide in 500 cm3 of diluted oven cleaner. _________________________________________________ [1] (iv) Calculate the number of moles of sodium hydroxide in 25.0 cm3 of the undiluted oven cleaner. _________________________________________________ [1] (v) Calculate the concentration of sodium hydroxide in the undiluted oven cleaner in mol dm 3. _________________________________________________ [1] (vi) Calculate the concentration of sodium hydroxide in the undiluted oven cleaner in g dm 3. _________________________________________________ [1] (vii) Assuming the oven cleaner has a density of 1.0 g cm 3 calculate the percentage of sodium hydroxide by mass in the oven cleaner. ___________________________________________________ _________________________________________________ [1] 5278 4 [Turn over BLANK PAGE (Questions continue overleaf) 5278 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 A, 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 A by dissolving a spatula-measure of A in a test tube half-full of water. Warm gently. 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 3 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 3 cm3 of the ammonia solution to the test tube. 2 Make a solution of A by dissolving half a spatula-measure of A in a test tube half-full of nitric acid solution. Warm gently. 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 2 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 A: _______________________________________________________ _______________________________________________________ 5278 6 [Turn over (b) You are provided with an organic liquid labelled B. 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 B in a test tube and add 1 cm3 of water. 2 Place 10 drops of B on a watch glass placed on a heat proof mat and ignite it using a splint. 3 Add approximately 10 drops of B to a test tube one quarter full of bromine water and mix well. 4 Add 10 drops of B 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 B. _______________________________________________________ a functional group which is absent from B. ____________________________________________________ [29] 5278 7 [Turn over Section B 3 Examiner Only Marks Remark Planning (a) The empirical formula of an oxide of lead can be found by reducing the lead oxide using the apparatus below. Excess carbon monoxide burning Carbon monoxide Lead 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 lead? ___________________________________________________ _________________________________________________ [2] (iv) Explain why the carbon monoxide continues to be passed through the apparatus after all the lead oxide has been reduced. ___________________________________________________ _________________________________________________ [2] 5278 8 [Turn over (b) When 1.39 g of the lead oxide was reduced, 1.26 g of lead was formed. Examiner Only Marks Remark (i) What mass of oxygen was present in the lead oxide? _________________________________________________ [1] (ii) How many moles of oxygen were present in the lead oxide? _________________________________________________ [1] (iii) How many moles of lead were formed? _________________________________________________ [1] (iv) Calculate the empirical formula of the lead oxide. ___________________________________________________ _________________________________________________ [2] 5278 9 [Turn over (c) Lead can be extracted from the ore galena, which contains lead(II) sulphide (PbS). Examiner Only Marks Remark The galena is first heated in air to form lead(II) oxide and sulphur dioxide. The lead(II) oxide is then heated with coke to form lead and carbon dioxide. (i) Write the equation for the formation of the lead(II) oxide. _________________________________________________ [2] (ii) Write the equation for the formation of the lead. _________________________________________________ [1] (iii) A sample of galena weighing 20.32 g contains 8.5% by mass of lead(II) sulphide. Calculate the percentage of lead in the sample of galena using the following headings. Mass of lead(II) sulphide in the sample ___________________________________________________ Percentage of lead in lead(II) sulphide ___________________________________________________ Mass of lead in the sample ___________________________________________________ Percentage of lead in the sample _________________________________________________ [4] 5278 10 [Turn over 4 The liquid ester ethyl benzoate (boiling point 211 C) can be prepared by refluxing a mixture of ethanol, benzoic acid and concentrated sulphuric acid. Examiner Only Marks Remark (a) Explain what is meant by refluxing. _____________________________________________________ [1] (b) After refluxing, the mixture is distilled and an impure sample of the ester 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 ester could be obtained from the remaining liquid. ___________________________________________________ _________________________________________________ [2] 5278 11 [Turn over 5 A white solid is thought to be either sodium carbonate or sodium hydrogencarbonate. Examiner Only Marks Remark (a) Describe how you would carry out a flame test to show the presence of sodium ions in the white solid. State the flame colour expected. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [3] (b) Describe how you would confirm the presence of carbonate or hydrogencarbonate ions using dilute hydrochloric acid and confirm the identity of any gas given off. State any observations expected. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [3] (c) Describe how you would distinguish between the presence of carbonate and hydrogencarbonate ions. State any observations expected. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [3] THIS IS THE END OF THE QUESTION PAPER 5278 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. 5278

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Additional Info : GCE MAY 2010 : (AS 3) Module 3: Practical Examination 1- Revised
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