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GCE MAY 2006 : (AS 3) Practical Examination 2

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2006 Chemistry assessing Module 3: Practical Examination 2 ASC32 Assessment Unit AS 3 [ASC32] FRIDAY 19 MAY, MORNING 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 22.12.05BP 2 19.2.05PEG 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 material 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 ASC3aS6 2465 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 anion. 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 Describe the appearance of X. 2 (a) Make a solution of X by dissolving a half spatulameasure of X in a test tube half full of water. Place 1 cm3 of this solution in a test tube with 1 cm3 of dilute nitric acid and 1 cm3 of silver nitrate solution. (b) Add 2 cm3 of dilute ammonia solution to the test tube. 3 (a) Place a half spatula-measure of X on a watch-glass and add 3 drops of concentrated hydrochloric acid. (b) Use a clean loop of nichrome wire to place a small amount of this acidified sample of X in a blue Bunsen flame. (b) Test any gas evolved with damp Universal Indicator paper. Name the two salts in X ____________________________________________ 1 22.12.05BP 2 19.2.05PEG 4 (a) Place a spatula-measure of X in a test tube and add 2 cm3 of dilute sodium hydroxide solution, warm gently. ____________________________________________ ASC3aS6 2465 ASC3aS6 2465 2 [Turn over (b) You are supplied with three halobutanes labelled A, B and C. Carry out the experiment and complete the table below. Identify A, B and C. Experiment Observations Deductions A B B C Place 1 cm3 of A, B and C separately into three test tubes. Label the test tubes with their contents. Add 1 cm3 of ethanol and 1 cm3 of silver nitrate solution to each test tube. Place the three test tubes in a beaker of water heated to just below boiling point. Leave for 5 minutes. A C A is __________________________ B is __________________________ [25] 1 22.12.05BP 2 19.2.05PEG C is __________________________ ASC3aS6 2465 3 [Turn over 2 Titration (a) You are provided with: sodium thiosulphate solution of concentration 0.05 mol dm 3 a solution containing 2.00 g dm 3 of impure potassium iodate(V) solid potassium iodide (4 1.5 g portions) starch indicator sulphuric acid of concentration 1.0 mol dm 3 You are required to: (i) add the potassium iodide to the potassium iodate(V) solution, acidify the solution and titrate the liberated iodine with the sodium thiosulphate solution. (ii) use your results to determine the percentage purity of the potassium iodate(V). Procedure sodium thiosulphate solution potassium iodate(V) potassium iodide sulphuric acid n n n n n n n 1 22.12.05BP 2 19.2.05PEG n Rinse out a burette with the sodium thiosulphate solution. Fill the burette with the sodium thiosulphate solution. Rinse out the pipette with the potassium iodate(V) solution. Using the pipette and a pipette filler, place 25.0 cm3 of the potassium iodate(V) solution in the conical flask. Add 1.5 g of potassium iodide to the conical flask and swirl to dissolve. Add about 10 cm3 of 1.0 mol dm 3 sulphuric acid to the conical flask. Add the sodium thiosulphate solution from the burette until the mixture is pale yellow; add starch indicator and then continue adding the sodium thiosulphate solution until the end point is reached. Record the results of one rough and two accurate titrations in the table. ASC3aS6 2465 ASC3aS6 2465 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 observed at the end point of the titration. from __________________ to __________________ [1] (c) The equation for the reaction between iodate(V) ions and acidified iodide ions is: IO (aq) + 5I (aq) + 6H+(aq) 3I2(aq) + 3H2O(l) 3 The equation for the reaction between the thiosulphate ions and iodine is: 2S2O2 (aq) + I2(aq) S4O2 (aq) + 2I (aq) 3 6 (i) Complete the mole ratio: IO 3 mole ratio : 1 : I2 : S2O2 3 : [1] (ii) Calculate the number of moles of sodium thiosulphate in the average titre. 2 19.2.05PEG ______________________________________________________ 1 22.12.05BP ____________________________________________________ [2] ASC3aS6 2465 5 [Turn over (iii) Use the mole ratio to determine the number of moles of potassium iodate(V) present in 25.0 cm3 of solution. Examiner Only Marks Remark ____________________________________________________ [1] (iv) Calculate the number of moles of potassium iodate(V) present in 1.0 dm3 of solution. ____________________________________________________ [1] (v) Calculate the mass of potassium iodate(V) in 1.0 dm3 of solution. ______________________________________________________ ____________________________________________________ [2] (vi) Determine the percentage purity of the potassium iodate(V). ______________________________________________________ ______________________________________________________ 1 22.12.05BP 2 19.2.05PEG ____________________________________________________ [2] ASC3aS6 2465 6 [Turn over 3 Planning Examiner Only Marks Remark You are required to plan an experiment to determine the relative molecular mass of carbon dioxide gas. A U-tube containing sodium hydroxide is weighed and connected to a 100 cm3 gas syringe filled with carbon dioxide. The gas is then slowly passed through the sodium hydroxide and the U-tube is reweighed. A suitable arrangement for the apparatus is shown below: anhydrous sodium sulphate carbon dioxide sodium hydroxide (a) (i) Carbon dioxide is formed when hydrochloric acid is added to calcium carbonate. Draw and label the apparatus which could be used to generate carbon dioxide. [3] (ii) Write the equation for the reaction between hydrochloric acid and calcium carbonate. 1 22.12.05BP 2 19.2.05PEG ____________________________________________________ [2] ASC3aS6 2465 7 [Turn over (b) What is the purpose of the anhydrous sodium sulphate? Examiner Only Marks Remark __________________________________________________________ _______________________________________________________ [2] (c) Write the equation for the reaction of carbon dioxide with sodium hydroxide to form sodium carbonate. _______________________________________________________ [2] (d) The carbon dioxide is slowly pushed through the U-tube containing sodium hydroxide. (i) Suggest how the apparatus could be modified to ensure that all the carbon dioxide is absorbed. ______________________________________________________ ____________________________________________________ [1] (ii) Explain how you would show that all the carbon dioxide is absorbed by the sodium hydroxide. ______________________________________________________ ____________________________________________________ [2] (e) When 100 cm3 of carbon dioxide were fully absorbed the mass of the U-tube increased from 86.95 g to 87.13 g. Use the headings below to determine the relative molecular mass of carbon dioxide. (All measurements were made at 20 C and one atmosphere pressure.) mass of carbon dioxide _______________________________________ __________________________________________________________ 2 19.2.05PEG moles of carbon dioxide in 100 cm3 _____________________________ __________________________________________________________ 1 22.12.05BP relative molecular mass of carbon dioxide ________________________ _______________________________________________________ [3] ASC3aS6 2465 8 [Turn over (f) This experiment could be used to determine the relative molecular mass of ammonia by replacing sodium hydroxide with sulphuric acid. Examiner Only Marks Remark (i) Draw the apparatus which would allow 100 cm3 of ammonia, from a gas syringe, to be bubbled through dilute sulphuric acid. [2] (ii) Write the equation for the reaction of ammonia with sulphuric acid. ____________________________________________________ [1] (iii) Suggest a suitable test which would indicate that all the ammonia had been absorbed by the sulphuric acid. ______________________________________________________ 1 22.12.05BP 2 19.2.05PEG ____________________________________________________ [2] ASC3aS6 2465 9 [Turn over 4 Structured Examiner Only Marks Remark Methylpropene gas is prepared by heating 2-chloro-2-methylpropane using the apparatus shown below. mineral wool methylpropene heat water Mineral wool is soaked in 2-chloro-2-methylpropane and ethanolic potassium hydroxide. The mixture is heated and methylpropene is collected in a test tube. (a) (i) Draw the structure of 2-chloro-2-methylpropane showing all the bonds present. [1] (ii) Explain why 2-chloro-2-methylpropane is insoluble in water. 2 19.2.05PEG _____________________________________________________ 1 22.12.05BP ____________________________________________________ [1] ASC3aS6 2465 10 [Turn over (b) (i) Write the equation for the reaction of 2-chloro-2-methylpropane, C4H9Cl, with ethanolic potassium hydroxide. Examiner Only Marks Remark ____________________________________________________ [2] (ii) State the name of this type of reaction. ____________________________________________________ [1] (c) One potential danger associated with heating reagents and collecting a gaseous product over water is that after heating the water rises back up the delivery tube. (i) Explain why this happens. ____________________________________________________ [1] (ii) Suggest how this potential danger could be avoided. ____________________________________________________ [1] (d) Use the following steps to calculate the volume of gaseous methylpropene formed at 20 C and one atmosphere pressure from 2 cm3 of liquid 2-chloro-2-methylpropane, if its density is 0.8 g cm 3. mass of 2-chloro-2-methylpropane in 2 cm3 __________________________________________________________ moles of 2-chloro-2-methylpropane __________________________________________________________ moles of methylpropene __________________________________________________________ 2 19.2.05PEG volume of gaseous methylpropene. 1 22.12.05BP _______________________________________________________ [4] ASC3aS6 2465 11 [Turn over (e) Methylpropene is an unsaturated hydrocarbon. Examiner Only Marks Remark (i) Explain the term unsaturated. ____________________________________________________ [1] (ii) Describe a chemical test for unsaturation. ______________________________________________________ ____________________________________________________ [2] (f) 2-chloro-2-methylpropane will react with aqueous sodium hydroxide to form an alcohol. (i) State whether the alcohol formed is primary, secondary or tertiary ____________________________________________________ [1] (ii) Describe a practical test to confirm the type of alcohol which is formed. ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] (iii) Explain how you could demonstrate that the 2-chloro-2-methylpropane had completely reacted. ______________________________________________________ ______________________________________________________ 1 22.12.05BP 2 19.2.05PEG ____________________________________________________ [2] ASC3aS6 ASC3aS6 2465 12 [Turn over 1 22.12.05BP 2 19.2.05PEG THIS IS THE END OF THE QUESTION PAPER ASC3aS6 1814a ASC3aS6 2465 13 [Turn over 2 19.2.05PEG 1 22.12.05BP ASC3aS6 1814a ASC3aS6 2465 14 [Turn over ASC3aS6 1814a 15 1 22.12.05BP 2 19.2.05PEG 2 19.2.05PEG 1 22.12.05BP S 12/05 4200 302507(123) [Turn over

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Additional Info : Gce Chemistry May 2006 Assessment Unit AS 3 Module 3: Practical Examination 2
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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