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GCE MAY 2008 : (AS 3) Practical Examination 1

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ERRATUM NOTICE General Certi cate of Education (Advanced Subsidiary) Chemistry, Assessment Unit AS3, Module 3, Practical Examination 1 (ASC31) Monday 12 May, Afternoon Notice to Invigilator Before the start of the examination the following should be read to candidates. 1. Go to the Question Paper. (Pause) 2. Turn to page 3 of the Question Paper. (Pause) 3. Go to experiment number 5. (Pause) 4. The third line reads Add 10 drops of Y . (Pause) 5. This should read Add 10 drops of B . (Pause) Repeat 1. Go to the Question Paper. (Pause) 2. Turn to page 3 of the Question Paper. (Pause) 3. Go to experiment number 5. (Pause) 4. The third line reads Add 10 drops of Y . (Pause) 5. This should read Add 10 drops of B . (Pause) Please make this change in your question paper now. This is the end of the announcement. Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2008 Chemistry assessing Module 3: Practical Examination 1 ASC31 Assessment Unit AS 3 [ASC31] MONDAY 12 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. 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 ASC3S8 3697R Marks 1 Observation/deduction Safety goggles must be worn at all times during this practical examination. Care should be exercised, especially when using sodium hydroxide solution and concentrated hydrochloric acid. (a) You are provided with 2 g of a mixture, labelled A, which contains two salts with a common anion, but different cations. Carry out the following experiments on the mixture. Record your observations and deductions in the spaces below and identify the two salts in A. Experiment 1 Observations Deductions Describe the appearance of A. 2 (a) Add half a spatula-measure of A to a test tube half-full of sodium hydroxide solution and warm gently. (b) Test the gas evolved with damp Universal Indicator paper. (c) Test the gas evolved by dipping a glass rod into concentrated hydrochloric acid and holding it over the mouth of the test tube. 3 Dip a nichrome wire loop into concentrated hydrochloric acid; touch sample A with the wire, then hold it in a blue Bunsen flame. 4 Dissolve half a spatulameasure of A in about 2 cm3 of dilute nitric acid. Add 2 cm3 of barium chloride solution. Name the two salts present in A ______________________________________________ Name the two salts in X ASC3S8 3697R ______________________________________________ 2 [Turn over (b) You are provided with an organic liquid labelled B which has the formula C3H8O. Carry out the following experiments. Record your observations and deductions in the spaces below. Suggest a structure for B. On completion of your experiments, dispose of B in the container provided. Experiment Observations 1 Describe the liquid B. 2 Add 2 cm3 of B to 2 cm3 of water. 3 Place 5 drops of B on a watch glass placed on a heatproof mat and ignite using a splint. 4 Add 1 cm3 of dilute sulphuric acid to 2 cm3 of potassium dichromate solution. Add 10 drops of B and warm gently. 5 Deductions Add 1 cm3 of a solution of iodine in potassium iodide. Add 10 drops of Y followed by 1 cm3 of sodium hydroxide solution. Add 1 cm3 of sodium hypochlorite solution. Functional group in B ______________________________________________________ Class of compounds ______________________________________________________ Structure of B __________________________________________________ [25] ASC3S8 3697R 3 [Turn over 2 Titration (a) You are provided with: hydrochloric acid of unknown concentration, but approximately 2 mol dm 3, sodium carbonate solution of concentration 0.1 mol dm 3, methyl orange indicator. You are required to: (i) dilute the hydrochloric acid using a pipette and a volumetric flask. (ii) titrate the sodium carbonate solution against the diluted hydrochloric acid using methyl orange as indicator. Procedure (i) Dilution dilute hydrochloric acid Using the pipette and pipette filler, place 25.0 cm3 of the hydrochloric acid in a 250 cm3 volumetric flask. Add deionised water to the flask, inverting the flask as the level approaches the mark. Fill to the mark with deionised water. Stopper and mix well by inversion. (ii) Titration 0.1 mol dm 3 sodium carbonate solution diluted hydrochloric acid and methyl orange ASC3S8 3697R Rinse out the burette with the 0.1 mol dm 3 sodium carbonate solution. Fill the burette with 0.1 mol dm 3 sodium carbonate solution. Rinse out the pipette with diluted hydrochloric acid solution. Using the pipette and a pipette filler, place 25.0 cm3 of the diluted hydrochloric acid solution in the conical flask. Add 2 or 3 drops of the methyl orange indicator to the conical flask and titrate with the 0.1 mol dm 3 sodium carbonate 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 an equation for the reaction of hydrochloric acid with sodium carbonate. ___________________________________________________ [2] (ii) Using the average titre, calculate the number of moles of sodium carbonate used. ___________________________________________________ [1] 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (iii) Use the ratio in which the hydrochloric acid reacts with sodium carbonate to calculate the number of moles of hydrochloric acid present in 25.0 cm3 of diluted solution. _____________________________________________________ ___________________________________________________ [2] ASC3S8 3697R 5 [Turn over (iv) Calculate the number of moles of hydrochloric acid present in the 250 cm3 volumetric flask. Examiner Only Marks Remark _____________________________________________________ ___________________________________________________ [2] (v) Calculate the concentration, in mol dm 3, of the undiluted hydrochloric acid. ___________________________________________________ [1] (vi) Calculate the concentration, in g dm 3, of the undiluted hydrochloric acid. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA ___________________________________________________ [1] ASC3S8 3697R 6 [Turn over BLANK PAGE (Questions continue overleaf) ASC3S8 3697R 7 [Turn over 3 Planning Examiner Only Marks Remark You are required to plan an experiment to find the enthalpy of combustion of a series of simple alcohols using a simple calorimeter. Apparatus I or II could be used to carry out the experiment. thermometer thermometer water water B screen B screen A A ethanol ethanol I II (a) (i) State the purpose of the two pieces of apparatus labelled A. ___________________________________________________ [1] (ii) Explain why the piece of apparatus labelled A in apparatus II is more efficient than that in apparatus I. ___________________________________________________ [1] (iii) Explain why the piece of apparatus labelled B in apparatus II is more efficient than that in apparatus I. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA ___________________________________________________ [1] (iv) Explain the purpose of the screens. ___________________________________________________ [1] ASC3S8 3697R 8 [Turn over (b) The following results were obtained in an experiment using ethanol: Examiner Only Marks Initial mass of ethanol Final mass of ethanol Initial temperature Final temperature Mass of water Remark = 19.8 g = 19.6 g = 22 C = 33 C = 0.10 kg (i) What mass of ethanol was burned? ___________________________________________________ [1] (ii) How many moles of ethanol were burned? __________________________________________________ [1] (iii) What was the temperature rise during the experiment? __________________________________________________ [1] (iv) Calculate the molar enthalpy of combustion of ethanol. The specific heat capacity of water = 4.18 10 3 J kg 1 K 1 at 293 K. Heat received by water = mass of water temperature rise specific heat capacity of water. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (v) Explain why the theoretical value for the combustion of ethanol is different from the experimental value. ___________________________________________________ [1] ASC3S8 3697R 9 [Turn over (c) (i) Write the equation for the complete combustion of ethanol. Examiner Only Marks Remark __________________________________________________ [2] (ii) Name the gas produced, apart from water vapour, in the complete combustion of ethanol. __________________________________________________ [1] (iii) How would you confirm the identity of this gas using a chemical test? State what would be observed. _____________________________________________________ ___________________________________________________ [2] (d) When ethanol is used as a fuel in camping stoves, a black deposit of carbon is formed on the base of the cooking pots. When a small amount of water is added to the ethanol, and this mixture burned, no carbon deposit is observed. It has been suggested that the carbon reacts with steam to produce carbon monoxide together with another gas. (i) Write an equation for the incomplete combustion of ethanol, in which carbon is one of the products. __________________________________________________ [2] (ii) Suggest an equation for the reaction between carbon and steam. 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA __________________________________________________ [2] ASC3S8 3697R 10 [Turn over BLANK PAGE 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (Questions continue overleaf) ASC3S8 3697R 11 [Turn over 4 Structured Examiner Only Marks Remark The following method can be used to prepare 1-bromobutane: CH3CH2CH2CH2OH + HBr CH3CH2CH2CH2Br + H2O Mr = 74 Mr = 137 Place 3 cm3 of butan-1-ol (density = 0.8 g cm 3) in a 25 cm3 flask. Weigh out 4.0 g of sodium bromide and add it and 4.5 cm3 of water to the butan-1-ol. Add 3.5 cm3 of concentrated sulphuric acid to form hydrobromic acid in situ. Add boiling chips, attach a condenser to the flask, and reflux the mixture for 45 minutes. Replace the condenser with a distillation setup, and distil the 1-bromobutane and water at a temperature below 110 C into a 10 cm3 flask, cooled in an ice-water bath. Add about 1 g of sodium sulphate to the distillate, and swirl the mixture. Transfer the 1-bromobutane to a test tube, add 1.5 cm3 of conc. sulphuric acid. Mix the two layers thoroughly. Place the test tube in an ice-water bath and allow the layers to separate. Draw off the sulphuric acid and discard it into a beaker half-filled with ice. Add about 0.5 g of sodium sulphate to the 1-bromobutane, and after several minutes add 0.5 g of potassium carbonate and mix well. Transfer the 1-bromobutane to a 10 cm3 flask. Set up the distillation apparatus as before and distil. Determine the mass of product. (a) (i) Write an equation to show how the hydrobromic acid is formed. __________________________________________________ [2] (ii) Suggest the meaning of the term in situ. __________________________________________________ [1] (b) Why are boiling chips added? ______________________________________________________ [1] 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA (c) (i) Draw a labelled diagram of the apparatus used to reflux the mixture. [3] ASC3S8 3697R 12 [Turn over (ii) State three changes made to the apparatus in order to set it up for distillation. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (d) What is the function of the sodium sulphate? ______________________________________________________ [1] (e) Why should the receiver flask be clean and dry? ______________________________________________________ [2] (f) A student following these instructions obtained 3.55 g of 1-bromobutane. (i) Calculate the number of moles of butan-1-ol used. ___________________________________________________ [2] (ii) Calculate the number of moles of 1-bromobutane formed. ___________________________________________________ [1] (iii) Assuming that the hydrobromic acid was in excess, calculate the percentage yield of the 1-bromobutane. _____________________________________________________ _____________________________________________________ 1 12.01.07/ES 2 9.02.07/RTS 3 2.03.07/EA ___________________________________________________ [1] (g) Referring to practical and theoretical considerations, suggest why the percentage yield is not 100%. Practical _________________________________________________ _________________________________________________________ Theoretical _______________________________________________ ______________________________________________________ [3] ASC3S8 3697R 13 Examiner Only Marks Remark THIS IS THE END OF THE QUESTION PAPER ASC3S8 3697R 14 [Turn over S 6/07 528-005-1 [Turn over ADVANCED SUBSIDIARY (AS) General Certificate of Education 2008 Chemistry Assessment Unit AS 3 assessing Module 3: Practical Examinations 1 and 2 [ASC31] [ASC32] MONDAY 12 MAY AND FRIDAY 16 MAY APPARATUS AND MATERIALS LIST ASC3S8/ASC3aS8 3697.02 Advice for centres All chemicals used should be at least laboratory reagent specification and labelled with appropriate safety symbols, e.g. irritant. Apparatus and reagents should be available for the identification tests of the gases listed in Section 2.10 of the specification, i.e. H2, O2, Cl2, CO2, SO2, HCl, NH3. For centres running multiple sessions candidates for the later session should be supplied with clean, dry glassware. If it is not feasible then glassware from the first session should be thoroughly washed, rinsed with deionised water and allowed to drain. ASC3S8/ASC3aS8 3697.02 2 [Turn over Practical Examination 1 Each candidate must be supplied with safety goggles or glasses. Question No. 1 Each candidate must be supplied with: eight test tubes (125 mm length 16 mm OD would be suitable); a test tube holder; a test tube rack; a spatula; nichrome wire; a heat-proof mat; a Bunsen burner; a wooden splint; a glass rod; two watch-glasses; a wash bottle containing deionised water; three droppers with teats; about 3.0 g of a mixture of 1.5 g ammonium sulphate and 1.5 g anhydrous sodium sulphate in a 50/100 cm3 beaker labelled A; about 10 cm3 of dilute nitric acid in a reagent bottle/beaker labelled dilute nitric acid and irritant. This solution should be approximately 2 M; about 10 cm3 of barium nitrate solution in a reagent bottle/beaker labelled barium chloride solution. This solution should be approximately 0.1 M (20.8 g dm 3 for BaCl2); about 10 cm3 of concentrated hydrochloric acid in a stoppered reagent bottle labelled concentrated hydrochloric acid and corrosive/irritant; about 10 cm3 of propan-2-ol in a stoppered container labelled B and flammable; ASC3S8/ASC3aS8 3697.02 3 [Turn over about 5 cm3 of potassium dichromate(VI) solution in a stoppered reagent bottle labelled potassium dichromate(VI) solution and irritant. This solution should be about 0.1 M (29.4 g dm 3); about 5 cm3 of dilute sulphuric acid in a reagent bottle labelled dilute sulphuric acid and irritant. This solution should be approximately 1 mol dm 3; Universal indicator paper; about 10 cm3 of sodium hydroxide solution in a reagent bottle labelled dilute sodium hydroxide and corrosive/irritant. This solution should be approximately 0.5 mol dm 3; about 5 cm3 of a solution of iodine in potassium iodide (3.0 g of potassium iodide and 2.5 g of iodine in 100 cm3 of water) labelled iodine in potassium iodide; about 5 cm3 of sodium hypochlorite solution (1% w/v) labelled sodium hypochlorite solution and corrosive/irritant. Question No. 2 Each candidate must be supplied with: one 50 cm3 burette of at least class B quality; one 25 cm3 pipette of at least class B quality; one 250 cm3 volumetric flask; a safety pipette filler; three conical flasks of 250 cm3 capacity; a funnel for filling the burette (optional); a white tile or white paper; two beakers of 100 cm3 capacity; a wash bottle containing deionised/distilled water; a retort stand and clamp; 150 cm3 of 0.1 mol dm 3 sodium carbonate solution labelled sodium carbonate solution 0.1 mol dm 3 and corrosive/irritant; 150 cm3 of dilute hydrochloric acid labelled hydrochloric acid and irritant. The diluted acid should be approximately 2 mol dm 3 and can be prepared by the dilution of the concentrated acid; Phenolphthalein indicator. ASC3S8/ASC3aS8 3697.02 4 [Turn over Practical Examination 2 Each candidate must be supplied with safety goggles or glasses. Question No. 1 Each candidate must be supplied with: eight test tubes (125 mm length 16 mm OD would be suitable); a test tube holder; a test tube rack; a spatula; nichrome wire; a heat-proof mat; a Bunsen burner; a wooden splint; a glass rod; two watch-glasses; a wash bottle containing deionised water; three droppers with teats; about 3.0 g of a mixture of 1.5 g potassium chloride and 1.5 g ammonium chloride in a 50/100 cm3 beaker labelled X; about 10 cm3 of silver nitrate solution in a reagent bottle/beaker labelled silver nitrate solution. This solution should be approximately 0.1 M (17.0 g dm 3); about 10 cm3 of dilute nitric acid in a reagent bottle/beaker labelled dilute nitric acid and irritant. This solution should be approximately 2 M; about 10 cm3 of concentrated hydrochloric acid in a stoppered reagent bottle labelled concentrated hydrochloric acid and corrosive/irritant; about 10 cm3 of propan-1-ol in a stoppered container labelled B and flammable; about 5 cm3 of potassium dichromate(VI) solution in a stoppered reagent bottle labelled potassium dichromate(VI) solution and irritant. This solution should be about 0.1 M (29.4 g dm 3); ASC3S8/ASC3aS8 3697.02 5 [Turn over about 5 cm3 of dilute sulphuric acid in a reagent bottle labelled dilute sulphuric acid and irritant. This solution should be approximately 1 mol dm 3; Universal indicator paper; about 10 cm3 of sodium hydroxide solution in a reagent bottle labelled dilute sodium hydroxide and corrosive/irritant. This solution should be approximately 0.5 mol dm 3; about 5 cm3 of a solution of iodine in potassium iodide (3.0 g of potassium iodide and 2.5 g of iodine in 100 cm3 of water) labelled iodine in potassium iodide; about 5 cm3 of sodium hypochlorite solution (1% w/v) labelled sodium hypochlorite solution and corrosive/irritant. Question No. 2 Each candidate must be supplied with: one 50 cm3 burette of at least class B quality; one 25 cm3 pipette of at least class B quality; one 250 cm3 volumetric flask; a safety pipette filler; three conical flasks of 250 cm3 capacity; a funnel for filling the burette (optional); a white tile or white paper; two beakers of 100 cm3 capacity; a wash bottle containing deionised/distilled water; a retort stand and clamp; 150 cm3 of 0.1 mol dm 3 sodium hydroxide solution labelled sodium hydroxide solution 0.1 mol dm 3 and corrosive/irritant; 150 cm3 of dilute sulphuric acid labelled sulphuric acid and irritant. The diluted acid should be approximately 0.5 mol dm 3 and can be prepared by the dilution of the concentrated acid; Methyl orange indicator. ASC3S8/ASC3aS8 3697.02 6 [Turn over S 1/08 528-023-1 [Turn over

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Additional Info : Gce Chemistry May 2008 Assessment Unit AS 3 Module 3: Practical Examination 1
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