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GCE MAY 2006 : (A2 2) Analytical, Transition Metals and Further Organic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2006 assessing Module 5: Analytical, Transition Metals and Further Organic Chemistry A2C21 Chemistry Assessment Unit A2 2 [A2C21] FRIDAY 2 JUNE, MORNING TIME 1 hour 15 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all sixteen questions. Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering. Answer all six questions in Section B. Write your answers in the spaces provided in this question paper. For Examiner s use only Question Number Marks Section A 1 10 INFORMATION FOR CANDIDATES 1 22.11.05ES The total mark for this paper is 90. Quality of written communication will be assessed in question 14(c). In Section A all questions carry equal marks, i.e. two-marks for each question. In Section B the figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. Section B 11 12 13 14 15 16 Total Marks A2C2S6 Section A For each of the questions only one of the lettered responses (A D) is correct. Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet. 1 Which one of the following is the electronic structure for the titantium ion, Ti2+, in the ground state? A B C D 2 Which one of the following amino acids is optically active and produces a neutral solution when dissolved in water? A B C D 1 22.11.05ES 3 1s22s22p63s23p64s2 1s22s22p63s23p63d2 1s22s22p63s23p63d14s1 1s22s22p63s23p43d24s2 NH2CH2COOH NH2CHCOOH | CH3 NH2CHCOOH | (CH2)4 | NH2 NH2CHCOOH | CH2 | COOH Which one of the following statements about benzene is incorrect? A B C D A2C2S6 A total of six electrons per molecule are delocalised. All of the carbon-carbon bonds are the same length. The bond angles are all 120 . The empirical formula is C6H6. 2 [Turn over 4 Which one of the following analytical techniques depends upon electronic transitions between energy levels? A B C D 5 1.06 g of hydrated sodium carbonate, Na2CO3.10H2O, were neutralised by 12.5 cm3 of dilute hydrochloric acid. What is the concentration of the acid in g dm 3? A B C D 6 infra-red spectroscopy mass spectrometry n.m.r. spectroscopy visible spectroscopy 10.8 (1:1) 21.6 (correct) 29.2 (anhydrous, 1:1) 58.4 (anhydrous, 1:2) Which one of the following graphs represents the absorbance against volume in a colorimetry experiment for the solutions of copper(II) sulphate and ammonia given? B A absorbance absorbance 0 10 5 5 C 10 0.05M CuSO4(aq) 0 0.1M NH3(aq) 0 10 3.33 6.66 5 5 3.33 6.66 5 5 6.66 3.33 10 0.05 M CuSO4(aq) 0 0.1 M NH3(aq) D absorbance absorbance 5 5 10 0.1M CuSO4(aq) 0 0.05M NH3(aq) 0 10 6.66 3.33 10 0.1 M CuSO4(aq) 0 0.05 M NH3(aq) 1 22.11.05ES 0 10 A2C2S6 3 [Turn over 7 In which one of the following complex ions is the metal ion in the oxidation state +2? A B C D 8 The order of increasing basic strength for ammonia, phenylamine and propylamine is A B C D 9 [Cr(H2O)5OH]2+ [CuCl4]2 [Fe(SCN)(H2O)5]2+ [TiCl6]2 ammonia, phenylamine, propylamine phenylamine, propylamine, ammonia phenylamine, ammonia, propylamine propylamine, ammonia, phenylamine Methylamine reacts with excess ethanoyl chloride according to the equation: CH3COCl + CH3NH2 CH3NHCOCH3 + HCl 6.00 g of N-methyl ethanamide were produced from 4.24 g of methylamine. What is the percentage yield? A B C D 60.0% (correct) 66.0% (use ethanoyl chloride etc) 70.6% (use mass) 78.6% 10 26.65 g of [Cr(H2O)5]3+.2Cl .H2O were dissolved in water. The solution was treated with excess silver nitrate solution. What mass of silver chloride precipitate was formed? 7.17 g (2:1 ratio) 14.35 g (only 1 Cl) 28.70 g (correct) 43.05 g (3 Cl) 1 22.11.05ES A B C D A2C2S6 4 [Turn over BLANK PAGE 1 22.11.05ES (Questions continue overleaf) A2C2S6 5 [Turn over Section B Examiner Only Marks Remark Answer all six questions in the spaces provided. 11 Platinum finds extensive use in medicine, for example in cisplatin, and as a catalyst in industry. (a) (i) Draw the structure of cisplatin. [2] (ii) State one use of cisplatin in medicine. __________________________________________________ [1] (b) A mixture of ammonia and oxygen is both kinetically and thermodynamically stable. The reaction between ammonia and oxygen is catalysed by platinum. (i) State the effect of platinum on the thermodynamic and kinetic stability of this mixture. thermodynamic stability _________________________________ __________________________________________________ [1] kinetic stability ________________________________________ __________________________________________________ [1] (ii) The reaction produces nitrogen(II) oxide and steam. Write the equation for this reaction. 1 22.11.05ES __________________________________________________ [2] A2C2S6 6 [Turn over 12 Toluene (methylbenzene), C6H5CH3, is used to make artificial sweeteners, pharmaceuticals and explosives. Examiner Only Marks Remark (a) Monobromination of the aromatic ring in toluene results in three possible structural isomers. (i) Draw two of the structural isomers. [2] (ii) Name a suitable catalyst for this reaction. __________________________________________________ [1] (iii) Explain why toluene undergoes substitution rather than addition with bromine. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (b) The explosive trinitrotoluene (TNT) is prepared by refluxing toluene with a nitrating mixture containing the NO2+ ion. (i) Name the NO2+ ion. __________________________________________________ [1] (ii) Name the two reagents used in the nitrating mixture. _____________________________________________________ __________________________________________________ [2] 1 22.11.05ES (iii) Draw a flow scheme for the mechanism of the mononitration of toluene. [3] A2C2S6 7 [Turn over 13 Proteins are synthesised from 20 essential amino acids. Recent research has shown that some organisms also use another amino acid called selenocysteine, which is shown below. Examiner Only Marks Remark H | NH2 C COOH | CH2SeH (a) (i) Explain why selenocysteine, like other amino acids, has a high melting point. _____________________________________________________ __________________________________________________ [2] (ii) State and explain if selenocsyteine is optically active. _____________________________________________________ __________________________________________________ [2] (b) Selenocysteine reacts with sodium carbonate solution. Write an equation for the reaction. ______________________________________________________ [2] (c) Some E. coli bacteria contain selenoproteins which are enzymes. (i) Draw the structure of the dimer formed between two selenocysteine molecules and circle the peptide link. 1 22.11.05ES [3] A2C2S6 8 [Turn over (ii) Explain the mechanism by which an enzyme acts. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (iii) On the axes below sketch how the enzyme activity is affected by altering the pH. activity [1] 1 22.11.05ES pH A2C2S6 9 [Turn over 14 Industrial wastewater often contains dissolved metals, such as copper, which must be reduced to low, non-toxic levels before discharge into rivers. Examiner Only Marks Remark (a) State how you could detect the presence of aqueous copper(II) ions in the untreated wastewater. _________________________________________________________ ______________________________________________________ [2] (b) Suggest how copper(II) ions may be removed from industrial wastewater. ______________________________________________________ [1] (c) Describe how you could use a titrimetric technique to determine the concentration of copper(II) ions in the effluent water. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [5] [2] 1 22.11.05ES Quality of written communication A2C2S6 10 [Turn over 15 The homologous series of alcohols can be ascended using a suitable synthetic route e.g. ethanol is converted to propan-1-ol as follows: Examiner Only Marks Remark HBr A CH3CH2OH CH3CH2Br CH3CH2CN B CH3CH2CH2NH2 C CH3CH2CH2OH (a) State the name, or formula, of the reagents required for steps A, B and C. A _______________________________________________________ B _______________________________________________________ C ____________________________________________________ [3] (b) A mass spectrometer can be used to distinguish between ethanol and propan-1-ol. (i) Identify the ion which would give rise to a peak at m/e = 17 for both ethanol and propan-1-ol. __________________________________________________ [1] (ii) Suggest one ion which may be detected in the mass spectrum of propan-1-ol but not for ethanol. 1 22.11.05ES __________________________________________________ [1] A2C2S6 11 [Turn over (c) The first step involves conversion of ethanol to bromoethane. The n.m.r. spectra of these compounds are shown below. 9 8 7 6 5 ethanol 4 3 2 1 Examiner Only Marks Remark 0 Source: http://www.steve.gb.com/images/science/ethanol_nmr_spectrum.png a b Br-CH2CH3 b a 5.0 4.0 3.0 2.0 1.0 0 ppm bromoethane 1 22.11.05ES Source: http://www.brynmawr.edu/Acads/Chem/mnerzsto/Image16.gif A2C2S6 12 [Turn over Compare and contrast these two spectra with particular reference to chemical shift, peak integration and spin-spin splitting. Examiner Only Marks Remark chemical shift _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] peak integration _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] spin-spin splitting _________________________________________________________ _________________________________________________________ _________________________________________________________ 1 22.11.05ES ______________________________________________________ [2] A2C2S6 13 [Turn over 16 Colour plays an important part in chemistry whether to perform analytical tests or to manipulate molecular structures to achieve desired shades. Examiner Only Marks Remark (a) State a chemical test for iron(II) ions in solution. _________________________________________________________ ______________________________________________________ [2] (b) The colour of a transition metal complex is affected by the ligands attached to the metal ion. This is illustrated by the following equilibrium: [Cu(H3O)6]2+(aq) + 4Cl (aq) [CuCl4]2 (aq) + 6H2O(l) (i) State the colour of the two copper complexes. [Cu(H3O)6]2+(aq) ______________________________________ [CuCl4]2 (aq) _______________________________________ [2] (ii) State the shape of the hexaaquacopper(II) ion. __________________________________________________ [1] (iii) Name a suitable reagent which could be added to the equilibrium to shift it to the right. __________________________________________________ [1] (c) 1,2-diaminoethane is a bidentate ligand which complexes with aqueous nickel(II) ions. (i) Draw the structure of 1,2-diaminoethane. 1 22.11.05ES [1] A2C2S6 14 [Turn over (ii) Suggest what is meant by the term bidentate ligand. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (iii) State the colour and formula of the complex formed when excess 1,2-diaminoethane (represented as en ) is added to aqueous nickel(II) ions. colour _______________________________________________ formula ___________________________________________ [2] (d) Chrysoidine was the first commercially useful azo dye. It was produced by the reaction of 1,3,5-triaminobenzene and benzene diazonium chloride. (i) Draw the structure of Chrysoidine, circling the azo group. [3] (ii) Explain why Chrysoidine is coloured. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (iii) Other functional groups may be incorporated onto the benzene ring. Suggest one reason why altering the attached functional group may be useful in the dyestuffs industry. 1 22.11.05ES __________________________________________________ [1] A2C2S6 15 [Turn over (e) Benzenediazonium chloride reacts with aqueous sodium sulphite to produce phenylhydrazine. Examiner Only Marks Remark C6H5N2Cl + 2Na2SO3 + 2H2O C6H5NHNH2 + 2Na2SO4 + HCl (i) State the role of sodium sulphite in this reaction. __________________________________________________ [1] (ii) In an experiment the yield of phenylhydrazine was 45.36 g. Calculate the volume of 2 M sodium sulphite solution required to produce this amount assuming an 80% yield. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ 1 22.11.05ES __________________________________________________ [4] A2C2S6 16 [Turn over 1 22.11.05ES BLANK PAGE A2C2S6 17 1 22.11.05ES BLANK PAGE A2C2S6 18 [Turn over 1 22.11.05ES BLANK PAGE A2C2S6 19 1 22.11.05ES S 11/05 0000 302507(118) [Turn over

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Additional Info : Gce Chemistry May 2006 Assessment Unit A2 1Module 5: Analytical, Transition Metals and Further Organic Chemistry
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