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GCE MAY 2009 : (A2 2) Analytical, Transition Metals and Further Organic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2009 Chemistry assessing Module 5: Analytical, Transition Metals and Further Organic Chemistry A2C21 Assessment Unit A2 2 [A2C21] WEDNESDAY 27 MAY, AFTERNOON 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 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 The total mark for this paper is 90. Quality of written communication will be assessed in question 15(f)(vi). 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. 4591 Section B 11 12 13 14 15 16 Total Marks BLANK PAGE 4591 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 Which one of the following is the electronic structure of the Co2+ ion in the ground state? 3d A [Ar] C [Ar] D 2 [Ar] B [Ar] Which one of the following gives the order of increasing basic strength for ammonia, ethylamine and phenylamine? A B C D 3 The folding of the -helix. The formation of a -pleated sheet. The sequence of amino acids. The coiling of the chains. The mechanism for the bromination of benzene is described as A B C D 4591 ammonia, phenylamine, ethylamine ethylamine, ammonia, phenylamine phenylamine, ammonia, ethylamine phenylamine, ethylamine, ammonia Which one of the following statements describes the primary structure of a protein? A B C D 4 4s electrophilic addition. electrophilic substitution. nucleophilic addition. nucleophilic substitution. 3 [Turn over 5 20 cm3 of a hydrocarbon CxHy were exploded in excess oxygen. The total volume of gases after reaction was found to be 50 cm3 lower than at the start. On bubbling through sodium hydroxide solution a further contraction of 80 cm3 occurred, all measurements were at 20 C and one atmosphere pressure. The formula of the hydrocarbon was A B C D 6 Iodoethane may be converted to propylamine by reaction with A B C D 7 C2H4 C2H6 C4H6 C4H8 ammonia. ammonia followed by lithal, LiAlH4. potassium cyanide followed by ammonia. potassium cyanide followed by lithal, LiAlH4. The fertiliser ammonium sulphate is manufactured according to the equation: H2SO4(aq) + 2NH3(g) (NH4)2SO4(aq) Which one of the following mixtures will produce the greatest mass of ammonium sulphate? (1 tonne = 1000 kg) mass of sulphuric acid/tonne A 6 5 5 C 8 2 D 9 1 Which one of the following nickel complexes is the most stable? A B C D 4591 4 B 8 mass of ammonia/tonne [Ni(H2O)6]2+ [Ni(NH3)6]2+ [Ni(en)3]2+ [Ni(edta)]2 4 [Turn over 9 Which one of the following reagents will not produce a precipitate when a few drops are added to separate samples of iron(III) sulphate solution? A B C D ammonia solution barium chloride solution potassium thiocyanate solution sodium hydroxide solution 10 Which one of the following processes does not involve any redox reactions? A B C D 4591 Decomposition of OCl ions using Co2+ ions. Determination of magnesium ions in solution using edta. Determination of the percentage of iron in aluminium foil. Preparation of potassium dichromate from chromium(III) ions. 5 [Turn over Section B Examiner Only Marks Remark Answer all six questions in the spaces provided. 11 (a) Complete the flow scheme below by writing the formulae of the three compounds formed. excess NH3(aq) conc. HCl Cu2+(aq) NaOH(aq) [3] (b) Copper(II) sulphate solution reacts with aqueous barium nitrate to form a white precipitate. Write the equation for this reaction. _______________________________________________________ [1] 12 The mass spectrum of 2-chloropropane, CH3CHClCH3, is shown below. 100 Relative Intensity 80 60 40 20 0 10 20 30 40 50 60 70 80 m/z (a) (i) Suggest why two molecular ion peaks are present in the spectrum. _____________________________________________________ ___________________________________________________ [1] 4591 6 [Turn over (ii) State the formula for the species giving rise to the peak at m/e = 63. Examiner Only Marks Remark ___________________________________________________ [1] (b) The n.m.r. spectrum of 2-chloropropane contains two sets of peaks as shown below. b a a 5 4 3 2 1 0 (i) Explain the peak integration. _____________________________________________________ ___________________________________________________ [2] (ii) Explain the chemical shifts. _____________________________________________________ ___________________________________________________ [1] (iii) Explain the splitting pattern a. _____________________________________________________ _____________________________________________________ ___________________________________________________ [1] (iv) Explain why b is a doublet. _____________________________________________________ _____________________________________________________ ___________________________________________________ [1] 4591 7 [Turn over 13 Vanadium is a characteristic transition metal showing variable oxidation states and catalytic action. Examiner Only Marks Remark (a) The following change occurs when a solution containing VO2+ ions is shaken with zinc amalgam. VO2+(aq) VO2+(aq) Deduce the oxidation state of vanadium in each of the two species and hence state the role of the zinc amalgam in the reaction. VO2+ ________________ VO2+ ________________ _______________________________________________________ [3] (b) Vanadium pentoxide is used as a solid heterogeneous catalyst in the Contact process, catalysing the conversion of sulphur dioxide to sulphur trioxide. 2SO2(g) + O2(g) 2SO3(g) (i) Explain the term heterogeneous. ___________________________________________________ [1] (ii) Explain in terms of surface chemistry how the vanadium pentoxide catalyses the above reaction. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] 4591 8 [Turn over (c) Vanadium(III) sulphate dissolves in water to form a green solution. Examiner Only Marks Remark (i) State the formula of vanadium(III) sulphate. ___________________________________________________ [1] (ii) Suggest the formula of hydrated vanadium(III) ions in aqueous solution and state the shape of this complex ion. _____________________________________________________ ___________________________________________________ [2] 4591 9 [Turn over 14 In the 19th century, used tea leaves were often recycled by boiling with iron(II) sulphate and sheep dung before being coloured with compounds such as Prussian Blue. Examiner Only Marks Remark (a) Prussian Blue, KFe[Fe(CN)6], may be prepared by adding potassium ferrocyanide solution, K4[Fe(CN)6], to a suitable aqueous iron salt. (i) Identify the ions present in potassium ferrocyanide solution. ___________________________________________________ [2] (ii) Suggest a suitable iron salt to react with potassium ferrocyanide in the preparation of Prussian Blue. ___________________________________________________ [1] (b) Drinks made with this recycled tea contained aqueous iron(II) ions. The concentration of iron(II) ions in solution can be determined by titration with standard potassium manganate(VII) solution. MnO4 (aq) + 5Fe2+(aq) + 8H+(aq) 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) (i) State the colour change noted at the end point of the titration. ___________________________________________________ [2] (ii) Calculate the volume of 0.1 M potassium manganate(VII) solution required to react with 25.0 cm3 of a solution which contains 7.84 g of iron(II) ions per litre. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 4591 10 [Turn over (c) Iron(II) sulphate and ammonium sulphate combine to form the double salt iron(II) ammonium sulphate, FeSO4.(NH4)2SO4.6H2O. Examiner Only Marks Remark (i) Describe how a back titration may be used to determine the percentage of ammonia in a sample of ammonium sulphate (details of calculations are not required). You may assume all apparatus used is clean and dry. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [4] (ii) Suggest why this method would be unsuitable for determining the percentage of ammonia in the double salt. _____________________________________________________ ___________________________________________________ [2] (iii) Calculate the mass of iron(II) sulphate required to make 20.0 g of the double salt. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 4591 11 [Turn over 15 Aromatic chemistry is a branch of organic chemistry which includes those compounds with 6-membered ring structures such as benzene and methylbenzene (toluene), C6H5CH3. Examiner Only Marks Remark (a) Name the industrial source of benzene. _______________________________________________________ [1] (b) State the empirical formula of benzene. _______________________________________________________ [1] (c) Describe the bonding present in benzene. _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (d) Benzene may be converted to methylbenzene (toluene) by reaction with chloromethane in the presence of aluminium chloride. C6H6 + CH3Cl C6H5CH3 + HCl The mechanism is similar to that for the nitration of benzene. (i) Suggest the function of the aluminium chloride. ___________________________________________________ [1] (ii) Suggest the formula of the species which attacks the benzene ring. ___________________________________________________ [1] 4591 12 [Turn over (e) Nitration of benzene forms nitrobenzene, C6H5NO2. Examiner Only Marks Remark (i) Name the reagents used for the nitration of benzene. _____________________________________________________ ___________________________________________________ [2] (ii) Further nitration results in the formation of dinitrobenzene. Draw and name the structure of one of the three possible isomers of dinitrobenzene. [2] (iii) State the reagents and conditions for the reduction of nitrobenzene to phenylamine. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] 4591 13 [Turn over (f) Phenylamine reacts with a mixture of sodium nitrite and hydrochloric acid to form benzene diazonium chloride. The benzene diazonium ion forms a scarlet precipitate of azo-2-naphthol when added to an alkaline solution of 2-naphthol. Examiner Only Marks Remark OH 2-naphthol (i) Sodium nitrite and hydrochloric acid react to form nitrous acid in situ. Write the equation for this reaction. ___________________________________________________ [1] (ii) Draw the structure of the benzene diazonium ion. [2] (iii) Explain why ethylamine does not form such a diazonium ion. _____________________________________________________ ___________________________________________________ [1] (iv) Name the type of reaction between benzene diazonium chloride and 2-naphthol to form the azo-2-naphthol. ___________________________________________________ [1] (v) Deduce the molecular formula of azo-2-naphthol. ___________________________________________________ [1] 4591 14 [Turn over (vi) Explain, in terms of electron transitions, why azo dyes are coloured. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] Quality of written communication 4591 [2] 15 [Turn over 16 Kevlar is used to make bullet-proof vests. The first step in its production is the polymerisation of the two monomers shown below: H2N NH2 benzene -1,4-diamine HOOC Examiner Only Marks Remark COOH benzene -1,4-dicarboxylic acid (a) State how infra-red spectroscopy could be used to distinguish between the two monomers. _________________________________________________________ _______________________________________________________ [2] (b) Write an equation for the reaction between benzene-1,4-dicarboxylic acid and excess sodium carbonate solution. _______________________________________________________ [2] (c) (i) Draw the structure of the dimer formed between the two monomers. [1] (ii) Name the link formed between the two monomers. ___________________________________________________ [1] (iii) Kevlar is a very strong and rigid material. Suggest why this polymer exhibits such properties. _____________________________________________________ ___________________________________________________ [2] THIS IS THE END OF THE QUESTION PAPER 4591 16 [Turn over 937-048-1 [Turn over

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Additional Info : Gce Chemistry May 2009 Assessment Unit A2 1Module 5: Analytical, Transition Metals and Further Organic Chemistry
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