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GCE JAN 2010 : (A2 2) Analytical, Transition Metals and Further Organic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education January 2010 assessing Module 5: Analytical, Transition Metals and Further Organic Chemistry [A2C21] A2C21 Assessment Unit A2 2 *A2C21* Chemistry WEDNESDAY 27 JANUARY, 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 fourteen 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 four questions in Section B. Write your answers in the spaces provided in this question paper. INFORMATION FOR CANDIDATES For Examiner s use only Question Number Marks Section A The total mark for this paper is 90. Quality of written communication will be assessed in question 14(d). 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. 1 10 5863 Total Marks Section B 11 12 13 14 BLANK PAGE 5863 2 [Turn over 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 How many electrons are there in the delocalised electron system in a benzene ring? A B C D 2 3 6 9 12 Which one of the following molecules is not planar? A C 3 Pt(NH3)2Cl2 infra-red spectroscopy mass spectroscopy n.m.r. spectroscopy ultra-violet spectroscopy The formation of the -helix. The folding of the -helix. The sequence of the amino acids. The sequence of the peptide links. The mechanism for the formation of nitrobenzene from benzene is described as A B C D 5863 D Which one of the following statements describes the secondary structure of a protein? A B C D 5 BF3 CCl4 Which one of the following spectroscopic techniques involves the breaking of bonds? A B C D 4 B electrophilic addition. electrophilic substitution. nucleophilic addition. nucleophilic substitution. 3 [Turn over Which one of the following describes the charge and coordination number of nickel in the [Ni(edta)]2 complex? A B C D A 50 cm3 sample of a gaseous hydrocarbon required exactly 250 cm3 of oxygen for complete combustion and produced 150 cm3 of carbon dioxide. All measurements of volumes were made under the same conditions. Which one of the following is the correct formula of the hydrocarbon? A B C D What is the total number of isomers of dibromobenzene, C6H4Br2? A B C D Which one of the following complexes is used as an anti-cancer drug? A H 3N NH3 B 5863 Cl2 NH3 Cl H 3N Cl D Cl Pt Pt H 3N NH2 H 2N NH3 Pt Cl Cl C Pt Cl 9 2 3 4 5 8 C3H4 C3H8 C5H10 C5H12 7 Coordination number 1 1 6 6 Charge 2+ 2 2+ 2 6 Cl2 4 [Turn over 10 The graph below shows the change in colour intensity when a 0.05 M solution of a metal ion X and a 0.025 M solution of a complexing ligand L are mixed in varying proportions. colour intensity 0 10 2 8 4 6 6 4 8 2 cm3 of 0.05 M cm3 of 0.025 M 10 0 X L The formula of the complex formed is A B C D 5863 XL2 XL4 XL8 X 2L 5 [Turn over Section B Examiner Only Marks Remark Answer all four questions in the spaces provided. 11 Complete the flow scheme below by writing the formulae of the three nickel compounds formed. OH Ni 2+ NH3 en [3] 12 Potassium manganate(VII) forms purple-red crystals which are soluble in water giving a deep purple solution. It is a powerful oxidising agent either as a solid or in solution. (a) When heated, potassium manganate(VII) decomposes to form oxygen. 2KMnO4 K2MnO4 + MnO2 + O2 The manganese compound MnO2 is a black insoluble solid whilst K2MnO4 is a soluble green solid. (i) Explain, with experimental details, how you would obtain a pure dry sample of MnO2 from the reaction mixture. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 5863 6 [Turn over (ii) Using oxidation numbers explain the redox changes when KMnO4 decomposes. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (iii) Calculate the volume of oxygen obtained at 20 C and one atmosphere pressure when 2.0 g of potassium manganate(VII) are completely decomposed. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (b) A solution of potassium manganate(VII) oxidises nitrites to nitrates. 6H2SO4 + 4KMnO4 + 5Ca(NO2)2 2K2SO4 + 4MnSO4 + 5Ca(NO3)2 + 6H2O (i) Rewrite this equation as an ionic equation. ___________________________________________________ [2] (ii) State the colour change observed. ___________________________________________________ [1] 5863 7 [Turn over (c) Potassium manganate(VII) may be used to determine the concentration of iron(II) ions in solution. The equation for the reaction is: Examiner Only Marks Remark MnO4 + 8H+ + 5Fe2+ Mn2+ + 4H2O + 5Fe3+ (i) A sample of steel (2.0 g) was dissolved in an excess of dilute sulphuric acid and the solution was made up to 250 cm3 with water. 25.0 cm3 samples of this solution were titrated with 0.02 M potassium manganate(VII) solution. The average titre was 34.9 cm3. Calculate the percentage of iron in the sample of steel. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (ii) An excess of sodium hydroxide solution was added to the titration flask after the titration was complete. Write three equations for the reactions taking place. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 5863 8 [Turn over 13 Phenylamine (aniline) was discovered in 1826 by distilling the dye indigo. The name aniline is derived from anil, the Portuguese word for indigo. Examiner Only Marks Remark NH2 aniline (a) Reduction of nitrobenzene produces aniline. Write the equation for the reduction of nitrobenzene using [H] to represent the reducing agent. _______________________________________________________ [2] (b) Aniline is basic and reacts with strong acids to form crystalline salts. (i) State the basicity of aniline compared to ammonia and phenylethylamine. CH2CH2NH2 phenylethylamine _______________________________________________________ [1] (ii) Write the equation for the reaction of aniline with hydrochloric acid. ___________________________________________________ [1] (iii) Explain why phenylethylamine is a primary amine. _____________________________________________________ ___________________________________________________ [1] 5863 9 [Turn over (c) The boiling point of aniline is 110 C, that of phenylethylamine is 195 C and propylbenzene is 159 C. Explain these relative boiling points in terms of intermolecular forces. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (d) When aniline is treated with nitrous acid at a low temperature the benzene diazonium ion is formed. NH2 + HNO2 H+ N2+ + 2H2O (i) Draw the structure of the benzene diazonium ion, C6H5N2+, showing all the bonds between the nitrogen atoms and the location of the charge. (Do not show the detailed structure of the benzene ring.) [2] (ii) Name the reagents used to generate the nitrous acid. ___________________________________________________ [2] (iii) If phenylethylamine is treated with nitrous acid under the same conditions the diazonium ion is not formed. Explain why. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] 5863 10 [Turn over (iv) If a solution of benzene diazonium ion is treated with aqueous sodium cyanide in the presence of a copper catalyst cyanobenzene is produced. Name the reagents A D in the flow scheme below. N2+ CN NaCN Examiner Only Marks Remark COOH A Cu B CH2NH2 CH2OH C CH2Cl D A _____________________________ B _____________________________ C _____________________________ D _____________________________ 5863 11 [4] [Turn over (e) The benzene diazonium ion reacts with a compound X to form compound Y, a red precipitate. Examiner Only Marks Remark OH N N compound Y (i) Suggest the structure of X. [1] ` (ii) Y is a conjugated molecule. Explain the meaning of the term conjugated. _____________________________________________________ ___________________________________________________ [2] (iii) Using the concept of conjugation and energy levels explain why Y is coloured. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 5863 12 [Turn over 14 Propanoic acid and ethyl methanoate are isomers which can be identified using spectroscopic techniques. Examiner Only Marks Remark (a) (i) Explain why propanoic acid and ethyl methanoate are regarded as isomers. _____________________________________________________ ___________________________________________________ [2] (ii) Write the equation for the formation of ethyl methanoate by an esterification reaction. ___________________________________________________ [2] (iii) This esterification is an equilibrium reaction. Explain how you would increase the yield of ethyl methanoate. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] 5863 13 [Turn over (b) The n.m.r. spectrum of ethyl methanoate is shown below. Examiner Only Marks 10 9 8 7 6 5 4 3 2 1 Remark 0 (i) Name the substance responsible for the signal at = 0 and state its formula. ___________________________________________________ [2] (ii) Explain the n.m.r. spectrum of ethyl methanoate with reference to spin spin splitting, peak integration and chemical shift. Spin spin splitting _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] Peak integration _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] Chemical shift _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] 5863 14 [Turn over (iii) Sketch the n.m.r. spectrum of propanoic acid on the chart below, labelling the peaks appropriately and showing the spin spin splitting together with peak integration. Examiner Only Marks Remark TMS [3] (c) The mass spectrum of ethyl methanoate is shown below. 100 31 28 80 relative 60 abundance 40 45 20 74 0 20 30 40 50 60 70 80 m/e Identify the ions responsible for the peaks. m/e 28 __________________ 45 5863 ion __________________ 15 [2] [Turn over (d) Explain how the absorption of radiation by molecules gives rise to infra-red spectra and how you would use infra-red spectroscopy to distinguish between propanoic acid and ethyl methanoate. Refer to specific bonds and their absorptions. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] Quality of written communication [2] THIS IS THE END OF THE QUESTION PAPER 5863 16 [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 noti ed. 5863

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Additional Info : Gce Chemistry January 2010 Assessment Unit A2 2 - Module 5: Analytical, Transition Metals and Further Organic Chemistry
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