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GCE MAY 2007 : (AS 3) Practical Examination 1

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2007 Chemistry assessing Module 3: Practical Examination 1 ASC31 Assessment Unit AS 3 [ASC31] TUESDAY 15 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 four questions. Write your answers in the spaces provided. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA INFORMATION FOR CANDIDATES The total mark for this paper is 90. Questions 1 and 2 are practical exercises each worth 25 marks. Question 3 is a planning exercise worth 20 marks. Question 4 is a written question testing aspects of experimental chemistry worth 20 marks. You may have access to notes, textbooks and other materials to assist you. A Periodic Table of Elements (including some data) is provided. For Examiner s use only Question Number 1 2 3 4 Total Marks ASC3S7 2926 Marks 1 Observation/deduction Safety goggles must be worn at all times and care should be exercised 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 (a) Make a solution of X by dissolving a half-spatula measure of X in a test tube half-full of dilute nitric acid. (b) Place one cm3 of the solution of X in a test tube with one cm3 of silver nitrate solution. (c) Place one cm3 of the solution of X in a test tube and add one cm3 of barium chloride solution. 2 (a) Using a fume cupboard, place a spatula measure of X in a test tube and add five drops of concentrated sulphuric acid. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (b) Test the gas given off with damp Universal Indicator paper. (c) Repeat part (a) in the fume cupboard, and test the gas given off using the stopper from a bottle of concentrated ammonia solution. 3 Place a half-spatula measure of X on a watch-glass and add three drops of concentrated hydrochloric acid. Use a clean loop of nichrome wire to place this acidified sample of X in a blue Bunsen flame. Name the two salts in X ______________________________________________ Name the two salts in X ______________________________________________ ASC3S7 2926 2 [Turn over (b) Y is an organic substance. Carry out the following experiments. Record your observations and deductions in the spaces provided. Identify the functional group present in Y. Experiment Observations Deductions 1 (i) Add two cm3 of Y to two cm3 of water in a test tube. (ii) Add three drops of Universal Indicator solution to the mixture. 2 Place 10 drops of Y on a watch-glass placed on a heatproof mat and ignite using a burning splint. 3 Add six drops of Y to two cm3 of acidified potassium dichromate(VI) solution in a test tube. Warm the mixture gently. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA Functional group present in Y _________________________________________________ [25] ASC3S7 2926 3 [Turn over 2 Titration The aim of the experiment is to determine the molarity of concentrated sulphuric acid and its concentration in g dm 3 by titrating a diluted sample of the acid with sodium hydroxide solution. The diluted sulphuric acid was made by adding 0.7 cm3 of concentrated sulphuric acid to distilled water and making the solution up to 250 cm3. (a) You are provided with: diluted sulphuric acid of unknown concentration, sodium hydroxide solution of concentration 0.1 mol dm 3, phenolphthalein indicator. You are required to: (i) titrate the sodium hydroxide against the diluted sulphuric acid using phenolphthalein as indicator. (ii) use your results to determine the molarity of concentrated sulphuric acid and consequently the mass of sulphuric acid per litre. Procedure sodium hydroxide solution diluted sulphuric acid + phenolphthalein indicator 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA ASC3S7 2926 Rinse out the burette with 0.1 mol dm 3 sodium hydroxide solution. Fill the burette with 0.1 mol dm 3 sodium hydroxide solution. Rinse out the pipette with the diluted sulphuric acid solution. Using the pipette and pipette filler, place 25.0 cm3 of the diluted sulphuric acid solution in the conical flask. Add three drops of the phenolphthalein indicator to the conical flask and titrate with 0.1 mol dm 3 sodium hydroxide solution until the end point is reached. Record the results of one rough and two accurate titrations in the table. 4 [Turn over Results Examiner Only Marks Initial burette reading/cm3 Final burette reading/cm3 Remark Titre/cm3 Rough 1st accurate 2nd accurate Average titre ___________ cm3 [15] (b) State the colour change at the end point. From __________________ to __________________ [1] (c) (i) Write the equation for the reaction of sulphuric acid with sodium hydroxide. __________________________________________________ [2] (ii) Using the average titre, calculate the number of moles of sodium hydroxide used. __________________________________________________ [1] (iii) Use the ratio in which sulphuric acid reacts with sodium hydroxide to calculate the number of moles of sulphuric acid present in 25.0 cm3 of the diluted acid. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA __________________________________________________ [1] (iv) Calculate the number of moles of sulphuric acid present in 0.7 cm3 of the concentrated acid. __________________________________________________ [1] (v) Calculate the number of moles of sulphuric acid present in 1 cm3 of the concentrated acid. __________________________________________________ [1] ASC3S7 2926 5 [Turn over (vi) Calculate the molarity of concentrated sulphuric acid. Examiner Only Marks Remark _________________________________________________ [1] (vii) Calculate the relative formula mass of sulphuric acid. _________________________________________________ [1] (viii) Calculate the number of grams of sulphuric acid in 1 dm3 of concentrated sulphuric acid. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA _________________________________________________ [1] ASC3S7 2926 6 [Turn over 3 Planning Examiner Only Marks Remark You are required to plan an experiment to identify a Group II metal carbonate, MCO3. A suitable amount of the carbonate is approximately 0.3 g. If this amount of metal carbonate is added to 50 cm3 of 0.1 mol dm 3 hydrochloric acid and the volume of carbon dioxide collected and measured, the identity of M can be determined. The equation for the reaction is: MCO3 + 2HCl MCl2 + H2O + CO2 (a) (i) Draw a labelled diagram of the apparatus which could be used to react the metal carbonate with the hydrochloric acid and to collect the carbon dioxide produced in a syringe. [3] (ii) The metal carbonate needs to be added quickly to the apparatus without gas being lost. Suggest how this may be carried out. __________________________________________________ [1] 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (iii) State one observation that could be made to show that the reaction has finished. _____________________________________________________ __________________________________________________ [1] ASC3S7 2926 7 [Turn over (iv) Suggest why it is better to collect the carbon dioxide in a syringe rather than over water. Examiner Only Marks Remark __________________________________________________ [1] (v) Explain why the carbon dioxide collected in the syringe is not pure. __________________________________________________ [1] (b) The metal carbonate is weighed using a suitable container. State the weighings which should be made. _________________________________________________________ ______________________________________________________ [2] (c) Suppose that 0.28 g of MCO3 gave 80 cm3 of carbon dioxide at 20 C and one atmosphere pressure. (i) Calculate the number of moles of carbon dioxide. __________________________________________________ [1] (ii) Calculate the number of moles of MCO3. __________________________________________________ [1] (iii) Calculate the relative formula mass of MCO3. __________________________________________________ [1] 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (iv) Calculate the relative atomic mass of M. __________________________________________________ [1] (v) Identify M. __________________________________________________ [1] ASC3S7 2926 8 [Turn over (d) An alternative way to determine the relative atomic mass of M would be to heat the metal carbonate. Examiner Only Marks Remark (i) Write the equation for the reaction including state symbols. __________________________________________________ [2] (ii) How would you determine when this reaction was complete? _____________________________________________________ __________________________________________________ [2] (iii) State the mass measurements that should be taken to determine the value of the relative atomic mass of M using this method. _____________________________________________________ 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA __________________________________________________ [2] ASC3S7 2926 9 [Turn over 4 Structured Examiner Only Marks Remark The preparation of 1-chlorohexane, C6H13Cl, from hexan-1-ol using thionyl chloride, SOCl2, is described below. Apart from the haloalkane, sulphur dioxide and hydrogen chloride are also produced. Assemble in a fume cupboard a 500-ml three-necked flask equipped with a sealed stirrer unit, a reflux condenser and a tap funnel; fit the condenser and the funnel with calcium chloride guard-tubes. Place 179 g (109.5 cm3) of redistilled thionyl chloride in the flask and 51 g (62.5 cm3) of hexan-1-ol, b.pt. 156 158 C, in the funnel. Add the alcohol with stirring over a period of 2 hours; there is a slight evolution of heat; sulphur dioxide and hydrogen chloride are evolved and the liquid darkens considerably. When all the alcohol has been added, reflux the mixture for 2 hours. Rearrange the apparatus for distillation and distil slowly. The excess thionyl chloride passes over below 80 C, followed by a small fraction up to 120 C and finally crude 1-chlorohexane at 132 134 C. Wash the 1-chlorohexane successively with water, 10% sodium carbonate solution and twice again with water. Dry with anhydrous calcium chloride and distil through a short fractionating column. Pure 1-chlorohexane passes over at 133 134 C. The yield is 36 g. (a) Write the equation for the formation of 1-chlorohexane from hexan-1-ol. ______________________________________________________ [1] (b) The production of the gases sulphur dioxide and hydrogen chloride can be confirmed by suitable chemical tests. (i) Describe how you could obtain a sample of the mixture of gases. __________________________________________________ [1] (ii) Describe a positive test for sulphur dioxide. _____________________________________________________ 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA __________________________________________________ [2] (c) Suggest the purpose of the guard-tubes which contain calcium chloride. ______________________________________________________ [1] ASC3S7 2926 10 [Turn over (d) The thionyl chloride has been redistilled. Examiner Only Marks Remark (i) What is the meaning of the term redistilled? __________________________________________________ [1] (ii) Suggest why the thionyl chloride has been redistilled. __________________________________________________ [1] (iii) Using the information provided, calculate the density of the redistilled thionyl chloride. _____________________________________________________ __________________________________________________ [2] (e) Suggest why the thionyl chloride is added over a period of 2 hours and not all at once. ______________________________________________________ [1] (f) The distilled 1-chlorohexane is washed with water and sodium carbonate solution. (i) Explain how the process of washing is carried out using a separating funnel. _____________________________________________________ _____________________________________________________ 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA __________________________________________________ [3] (ii) Suggest what is removed by the water. __________________________________________________ [1] ASC3S7 2926 11 [Turn over (g) Calculate the percentage yield using the following headings. Examiner Only Marks Remark (i) Relative formula mass of thionyl chloride. __________________________________________________ [1] (ii) Moles of thionyl chloride. __________________________________________________ [1] (iii) Relative formula mass of hexan-1-ol. __________________________________________________ [1] (iv) Moles of hexan-1-ol. __________________________________________________ [1] (v) Relative formula mass of 1-chlorohexane. __________________________________________________ [1] (vi) Percentage yield. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA __________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER ASC3S7 2926 12 [Turn over S 1/07 7-155-1 [Turn over 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA

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Additional Info : Gce Chemistry May 2007 Assessment Unit AS 3 Module 3: Practical Examination 1
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