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GCE MAY 2009 : (A2 3A) Synoptic Paper

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2009 Chemistry assessing Module 6A: Synoptic Paper A2C31 Assessment Unit A2 3A [A2C31] FRIDAY 29 MAY, MORNING TIME 1 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. Section A contains a Planning Exercise. Section B contains four questions assessing different aspects of the specification. INFORMATION FOR CANDIDATES The total mark for this paper is 80. Quality of written communication will be assessed in question 1. Figures in brackets printed down the right-hand side of pages indicate the mark awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. For Examiner s use only Question Number 1 2 3 4 5 Total Marks 4592 Marks Section A Examiner Only Marks 1 Remark Planning Exercise Preparation of antimony(III) bromide Antimony(III) bromide, SbBr3, is an off-white solid with a melting point of 97 C and a boiling point of 280 C. The solid is corrosive and is harmful by inhalation. It decomposes in water, but is soluble in organic solvents such as 1,1,1-trichloroethane. The elements, antimony and bromine, combine directly when heated together under reflux. You are provided with standard laboratory apparatus and the following chemicals: antimony granules bromine (density 3.1 g cm 3) 1,1,1-trichloroethane Plan how you could prepare 5 g of pure antimony(III) bromide based on the mass of bromine used. Your plan should include: (a) the relevant equation; _______________________________________________________ [2] (b) a calculation to show the volume of bromine needed assuming a 75% yield; _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] 4592 2 [Turn over (c) the procedure, including any relevant safety precautions, and observations made during the reaction; Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [8] (d) how to separate and purify the product and test its purity. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] Quality of written communication 4592 [2] 3 [Turn over Section B Examiner Only Marks Remark Answer all four questions in the spaces provided. 2 At the Kyoto Summit in 1997 an agreement was reached to limit pollution, including that due to sulphur hexafluoride, SF6, which is one of the most potent greenhouse gases. (a) The industrial preparation of sulphur hexafluoride involves the combustion of molten sulphur, S8, in fluorine. (i) Write an equation for this reaction including state symbols. ___________________________________________________ [2] (ii) The product is contaminated with disulphur decafluoride, S2F10, which disproportionates on heating: S2F10(g) SF6(g) + SF4(g) Explain, using the oxidation states of sulphur, how this reaction may be classified as disproportionation. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (iii) The sulphur tetrafluoride, SF4, is removed by alkaline hydrolysis forming sulphite ions, fluoride ions and water. Write an equation for this reaction. ___________________________________________________ [2] (iv) Describe how you could test for the presence of sulphite ions in solution. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 4592 4 [Turn over (b) Sulphur hexafluoride has a global warming effect that is 23 900 times greater than carbon dioxide. Examiner Only Marks Remark (i) Sulphur hexafluoride absorbs infra-red radiation. Describe two effects this absorbed radiation has on the covalent bonds in sulphur hexafluoride. _____________________________________________________ ___________________________________________________ [2] (ii) Calculate the volume of carbon dioxide, measured at 20 C and one atmosphere pressure, which will have the same global warming effect as 1 tonne of sulphur hexafluoride. (1 tonne = 1000 kg) _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 4592 5 [Turn over 3 Human urine is a complex mixture which includes urea, uric acid, hippuric acid and magnesium ions. Examiner Only Marks Remark (a) The hydrolysis of urea, NH2CONH2, produces ammonium carbonate as the only product and is catalysed by the enzyme urease. (i) Write an equation for this hydrolysis. ___________________________________________________ [1] (ii) Draw a labelled enthalpy level diagram to show the catalysed and uncatalysed reaction pathways. Assume the reaction is endothermic. enthalpy [2] (b) An excess accumulation of uric acid in the body can lead to a type of arthritis known as gout. Uric acid is a weak acid with a pKa value of 3.89. Calculate the pH of a 0.05 M solution of uric acid. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (c) Hippuric acid derives its name from the Greek word hippos which means horse, since the acid is found in relatively high concentrations in horses urine. The acid has the structure: O C NH CH2 OH C O 4592 6 [Turn over (i) Deduce the molecular formula of hippuric acid. Examiner Only Marks Remark [1] (ii) Explain why hippuric acid is soluble in water. [2] (iii) The acid can be hydrolysed to form benzoic acid and glycine. Explain why glycine is not optically active. [1] (d) The magnesium content of a sample of urine can be determined by titration with standard edta solution. (i) Name the indicator used in this titration and state the colour change at the end point. [2] (ii) Human urine typically contains 0.01 g of magnesium per 100 cm3. Calculate the volume of 0.02 M edta solution required to react completely with 100 cm3 of urine. [3] 4592 7 [Turn over 4 Propanone and propanal are structural isomers which, despite both containing a carbonyl group, exhibit significant differences in their chemistry. Examiner Only Marks Remark (a) The two compounds may be readily distinguished from one another by either chemical or spectroscopic means. (i) Describe how to distinguish between these two compounds using a suitable chemical reaction, naming any reagent(s) and noting expected observations. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (ii) How would n.m.r. spectroscopy distinguish between propanone and propanal? _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (b) Propanal reacts with hydrogen cyanide to form 2-hydroxybutanenitrile which itself may be hydrolysed as shown in the following flow scheme: OH OH HCN | | CH3CH2CHO CH3CH2 C H CH3CH2 C H STEP 1 | STEP 2 | CN COOH A (i) Draw a flow scheme for the mechanism in Step 1. [3] 4592 8 [Turn over (ii) Name a reagent used to hydrolyse the 2-hydroxybutanenitrile in Step 2. Examiner Only Marks Remark ___________________________________________________ [1] (iii) Give the systematic name for A. ___________________________________________________ [1] (c) Both aldehydes and ketones undergo a condensation reaction with hydroxylamine, NH2OH, in a similar way to 2,4-dinitrophenylhydrazine. (i) Draw the structure of the organic product formed when ethanal reacts with hydroxylamine. [1] (ii) An unknown ketone reacts with hydroxylamine to form a compound with the following composition: element % C 45.38 H 4.20 N 23.53 O 26.89 Deduce the empirical formula of the product. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 4592 9 [Turn over 5 Nitrogen forms five different oxides in addition to a number of ions in which nitrogen is joined to oxygen. Examiner Only Marks Remark (a) Nitrogen(II) oxide may be prepared by the action of 50% nitric acid on copper: 3Cu(s) + 2NO3 (aq) + 8H+(aq) 3Cu2+(aq) + 2NO(g) + 4H2O(l) (i) State two observations which can be made during this reaction. _____________________________________________________ ___________________________________________________ [2] (ii) Describe how you could test for the presence of copper(II) ions in solution. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (iii) Nitrogen(II) oxide reacts with chlorine according to the equation: 2NO(g) + Cl2(g) 2NOCl(g) The reaction is third order overall with a rate constant of 1.7 10 5 dm6 mol 2 s 1. Calculate the initial rate of reaction when the concentration of each reactant is 0.1 M. _____________________________________________________ ___________________________________________________ [2] (iv) Nitrogen(II) oxide reacts with ozone to form nitrogen(IV) oxide and oxygen. Write the equation for this reaction. ___________________________________________________ [1] 4592 10 [Turn over (b) Nitrogen(IV) oxide is able to dimerise according to the equilibrium: Examiner Only Marks 2NO2(g) Remark N2O4(g) H = 58 kJ mol 1 (i) State and explain the effect that lowering the temperature will have on the partial pressure of nitrogen(IV) oxide, NO2, at equilibrium. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) State the effect of increasing the total pressure on the position of the equilibrium. ___________________________________________________ [1] (c) Solid nitrogen(V) oxide, N2O5, is ionic, existing as NO+NO . 2 3 The NO+ ion has the same electronic structure as carbon dioxide. 2 (i) Name the NO+ ion. 2 ___________________________________________________ [1] (ii) Draw a dot and cross diagram to show the bonding in the NO+ ion. 2 [2] 4592 11 [Turn over (iii) The NO+ ion attacks the benzene ring in the nitration of toluene to 2 form trinitrotoluene. Examiner Only Marks Remark CH3 O2N NO2 NO2 trinitrotoluene Name the mechanism by which this nitration takes place and suggest the systematic name for trinitrotoluene. name of mechanism ___________________________________ [2] systematic name ______________________________________ [1] THIS IS THE END OF THE QUESTION PAPER 4592 12 [Turn over 0000 13 [Turn over 0000 14 [Turn over 0000 15 [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. 937-047-1

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Additional Info : Gce Chemistry May 2009 Assessment Unit A2 3A Module 6A: Synoptic Paper
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