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GCE MAY 2007 : (A2 3A) Synoptic Paper

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2007 Chemistry assessing Module 6A: Synoptic Paper A2C31 Assessment Unit A2 3A [A2C31] FRIDAY 1 JUNE, 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(f). 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 A2C3AS7 2902 Marks Section A 1 Planning Exercise Consider the following plan describing the synthesis of the dye Sudan I Na+O + N N HO N == N + sodium 2-naphtholate Sudan I Phenylamine is a carcinogen. Sodium nitrite and 2-naphthol are toxic. Step 1: Preparation of sodium 2-naphtholate solution: In a reaction flask, prepare a solution of 7.2 g of 2-naphthol in 10 cm3 of 3.0 mol dm 3 NaOH. Place this flask in an ice bath to cool until ready to use in Step 3. Step 2: Preparation of benzene diazonium chloride: Weigh 5.0 g of phenylamine in a 100 cm3 reaction flask and add 5.0 cm3 of concentrated hydrochloric acid and 10 cm3 of distilled water. Warm this solution to dissolve the phenylammonium chloride formed and then cool it in an ice bath. Prepare a solution of 1.0 g of sodium nitrite, NaNO2, in 10 cm3 of water. Add this solution drop-wise to the phenylammonium chloride solution while maintaining the reaction at ice bath temperature and agitating the mixture. Step 3: Preparation of Sudan I: Add the benzene diazonium chloride solution from Step 2 to the sodium 2-naphtholate solution from Step 1, while keeping both solutions at 0 5 C. After addition, leave the reaction mixture for 15 min with occasional stirring. Recrystallise the crude product from ethanol. Filter, dry, and weigh the product and determine its melting point. Typical yields are about 40 to 50%. A2C3AS7 2902 2 [Turn over (a) Write the equation for the reaction between phenylamine and nitrous acid. Examiner Only Marks Remark _______________________________________________________ [2] (b) Explain the safety precaution necessary for handling phenylamine. _________________________________________________________ _______________________________________________________ [1] (c) Draw a diagram of the apparatus used for adding sodium nitrite solution dropwise to the phenylammonium chloride solution while maintaining the reaction below 5 C. [3] (d) Calculate the mass of Sudan I which would be obtained from 7.2 g of 2-naphthol and 5.0 g of phenylamine, assuming a 50% yield. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] A2C3AS7 2902 3 [Turn over (e) Explain why both solutions in Step 3 must be kept at temperatures between 0 5 C. Examiner Only Marks Remark _________________________________________________________ _______________________________________________________ [1] (f) Give full experimental details of the recrystallisation of the Sudan I from ethanol. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] Quality of written communication [2] (g) Give full experimental details for the determination of the melting point of the Sudan I. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (h) How would you expect the melting point of the crude product to compare with that of the recrystallised Sudan I? _________________________________________________________ _______________________________________________________ [1] A2C3AS7 2902 4 [Turn over Section B Examiner Only Marks Remark Answer all four questions in the spaces provided. 2 Tulsiana has reported the isolation of glucosamine, galactose and glucose from a female rat s preputial gland. Glucosammonium sulphate is supplied by pharmacists as a treatment for arthritis: 2 SO4 CH2 OH O H H H OH H H HO NH 3 OH + 2 Glucosammonium sulphate (a) The glucosammonium ion, C6H11O5NH3+, has an acid dissociation constant, Ka, of 8.12 10 5 mol dm 3. (i) Write an expression for the dissociation constant of the glucosammonium ion. __________________________________________________ [1] (ii) Calculate the pKa of the glucosammonium ion. __________________________________________________ [1] (iii) Calculate the pH of a 0.2 mol dm 3 solution of C6H11O5NH3+. _____________________________________________________ _____________________________________________________ __________________________________________________ [3] A2C3AS7 2902 5 [Turn over (b) Glucosamine has five chiral centres. Explain the term chiral. Examiner Only Marks Remark _________________________________________________________ ______________________________________________________ [2] (c) (i) Describe what will be observed when a solution of glucosammonium sulphate is added to acidified barium chloride solution. __________________________________________________ [1] (ii) Write an ionic equation for the reaction. __________________________________________________ [1] (d) Kyung Hee Hong has studied the complex ion formed between copper(II) ions and glucosamine, the latter acting as a polydentate ligand. CH2 OH O H HO H OH H OH H H NH2 glucosamine (i) What type of bonds are formed between atoms in the glucosamine molecule and the copper(II) ion? __________________________________________________ [1] (ii) Explain the term polydentate ligand. _____________________________________________________ __________________________________________________ [2] A2C3AS7 2902 6 [Turn over (e) Glucose is a reducing sugar. Examiner Only Marks Remark (i) Describe and explain the reaction between glucose and Fehling s solution. _____________________________________________________ __________________________________________________ [2] (ii) What type of reaction occurs when lactose is heated with dilute sulphuric acid to form glucose and galactose? __________________________________________________ [1] A2C3AS7 2902 7 [Turn over 3 (a) Concentrated sulphuric acid is a dehydrating agent. The reaction between concentrated sulphuric acid and ethanol produces an ether, C4H10O, which has an alkyl group on either side of an oxygen atom. There are three isomeric forms of the ether. Examiner Only Marks Remark (i) Explain the term isomer. __________________________________________________ [1] (ii) Draw the structures for two of the isomers of the ether. [2] (iii) The n.m.r. spectrum of the ether is shown below. (iv) Deduce the structure of the ether, explaining your use of the integration curve and the splitting patterns. _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [4] A2C3AS7 2902 8 [Turn over (b) Concentrated sulphuric acid is used as a catalyst in the preparation of ethyl ethanoate. Examiner Only Marks Remark (i) Write the equation for the formation of ethyl ethanoate. __________________________________________________ [2] (ii) Write the equilibrium constant, Kc, for this reaction. __________________________________________________ [1] (iii) On the axes below, draw enthalpy profiles for the catalysed and uncatalysed reactions. enthalpy extent of reaction A2C3AS7 2902 9 [2] [Turn over (c) When concentrated sulphuric acid is heated, it behaves as an oxidising agent, reacting with metals such as copper, mercury and lead. Examiner Only Marks Remark (i) Use the standard electrode potentials below to calculate the electrode potential for the reaction between concentrated sulphuric acid and lead. Pb2+(aq) + Pb(s) 4H+ + SO42 + 2e E /V 0.13 2H2O + SO2 2e +0.17 __________________________________________________ [1] (ii) One of the products of the reaction, sulphur dioxide, may be identified by reaction with acidified potassium manganate(VII) solution. Describe what would be observed during the test and write the ionic equation for the reaction. _____________________________________________________ _____________________________________________________ __________________________________________________ [4] A2C3AS7 2902 10 [Turn over 4 Soy milk contains the following unsaturated fat. Examiner Only Marks Remark CH3(CH2)7 CH == CH(CH2)7 COO CH2 CH3(CH2)7 CH == CH(CH2)7 COO CH CH3(CH2)14COO CH2 Mr = 858 (a) (i) The degree of unsaturation of a fat is indicated by its iodine value. Describe how the iodine value of the fat in soy milk may be determined experimentally. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [4] (ii) Calculate the volume of hydrogen, measured at 20 C and 1 atmosphere pressure, needed to saturate 4.6 g of the fat. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (iii) Name and describe the physical state of the catalyst used in the hydrogenation of fats. _____________________________________________________ __________________________________________________ [2] A2C3AS7 2902 11 [Turn over (b) Soy milk can be made into tofu, a soft cheese-like food, by curdling through the addition of magnesium chloride. Examiner Only Marks Remark (i) The concentration of magnesium ions in tofu can be determined by titration with edta. Name a suitable indicator and state the colour change. _____________________________________________________ __________________________________________________ [3] (ii) 3.0 g of tofu is boiled with distilled water, filtered and made up to 100 cm3 in a volumetric flask. A 10.0 cm3 sample is titrated against a 0.01 mol dm 3 solution of the disodium salt of edta and 20.5 cm3 are required for the indicator to change colour. Calculate the percentage concentration of magnesium chloride in the sample. _____________________________________________________ _____________________________________________________ __________________________________________________ [4] A2C3AS7 2902 12 [Turn over 5 (a) Platinum, Pt, is a silvery-white metal when pure. It can be isolated from its ore as follows: Examiner Only Marks Remark Preliminary treatment of the ore with aqua regia (a mixture of concentrated hydrochloric and nitric acids) gives a solution containing H2PtCl6. The platinum is precipitated out as impure (NH4)2PtCl6 on treatment with NH4Cl. The (NH4)2PtCl6 yields platinum metal when strongly heated. (i) What is the oxidation number of platinum in H2PtCl6? __________________________________________________ [1] (ii) What is the co-ordination number of platinum in the complex ion PtCl62 ? __________________________________________________ [1] (iii) The concentrated nitric acid in the aqua regia initially oxidises the platinum to the +2 state in the same way that it oxidises copper. Suggest an equation for the reaction between concentrated nitric acid and platinum. __________________________________________________ [2] (b) The structure for the complex, cis-platin, is shown below: Cl NH3 Pt Cl NH3 (i) State a medical use for cis-platin. __________________________________________________ [1] (ii) Draw the structure of the trans isomer. [1] A2C3AS7 2902 13 [Turn over (iii) One of the side effects of treatment with cis-platin is an increase in uric acid in the body Examiner Only Marks Remark OH C N N C C C C OH HO N N H Uric acid Calculate the percentage of nitrogen in uric acid. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (iv) In the body, cis-platin is able to interact with proteins whose molecular arrangement may be described in terms of primary or secondary structure. Define these terms. Primary structure _______________________________________ ___________________________________________________ [1] Secondary structure _____________________________________ ___________________________________________________ [1] A2C3AS7 2902 14 [Turn over (c) Platinum, supported on aluminium oxide, is used to catalyse the reforming of hexane to benzene via chemisorption. Examiner Only Marks Remark (i) Explain the term chemisorption. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (ii) Suggest an equation for the reforming of hexane to benzene. __________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER A2C3AS7 2902 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. S 10/06 7-137-1

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Additional Info : Gce Chemistry May 2007 Assessment Unit A2 3A Module 6A: Synoptic Paper
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