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GCE JUN 2010 : (A2 2) Analytical, Transition Metals and Further Organic Chemistry - Revised

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Sp N ec e i w ca tio n Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2010 assessing Analytical, Transition Metals, Electrochemistry and Further Organic Chemistry [AC222] AC222 Assessment Unit A2 2 *AC222* Chemistry TUESDAY 1 JUNE, AFTERNOON TIME 2 hours. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all seventeen 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 seven questions in Section B. Write your answers in the spaces provided in this question paper. INFORMATION FOR CANDIDATES The total mark for this paper is 120. Quality of written communication will be assessed in question 16(b). 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. 5622 For Examiner s use only Question Number Marks Section A 1 10 Section B 11 12 13 14 15 16 17 Total Marks Section A For each of the following 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 The mass spectrum of methanol is shown below. Which one of the following is the base peak? C 100% B D Relative intensity A 25 30 35 m/e 2 Which one of the following represents the electronic configuration for the Fe3+ ion? A B C D 3 Which one of the following formulae cannot be determined by colorimetry? A B C D 5622 1s2 2s2 2p6 3s2 3p6 3d5 1s2 2s2 2p6 3s2 3p6 3d3 4s2 1s2 2s2 2p6 3s2 3p6 3d4 4s1 1s2 2s2 2p6 3s2 3p6 3d6 4s2 [Cu(NH3)4(H2O)2]2+ [Fe(SCN)(H2O)5]2+ [Ni(NH3)4(H2O)2]2+ [Zn(NH3)4(H2O)2]2+ 2 [Turn over 4 The standard electrode potentials for a series of redox equations are listed below. E /V Mn2+(aq) + 2e Mn(s) 1.19 Fe2+(aq) + 2e Fe(s) 0.44 Ni2+(aq) + 2e Ni(s) 0.25 I2(s) + 2e Fe3+(aq) + e Ag+(aq) + e 2I (aq) +0.54 Fe2+(aq) +0.77 Ag(s) +0.80 Which one of the elements listed will reduce Fe3+(aq) to Fe2+(aq), but not to Fe(s)? A B C D 5 Iodine Manganese Nickel Silver Which one of the following represents the structure of cisplatin? A NH3 Cl B Pt NH3 C NH3 NH3 Cl D Cl Pt Pt Cl NH3 NH3 Cl Pt H 2O NH3 NH3 5622 Cl 3 H 2O [Turn over 6 The nmr spectrum of a compound X is shown below. 5 4 3 2 1 0 Chemical shift, d Which one of the following is X? A B C D 7 CH3CH2CH2COOH CH3CH2COOCH2CH3 CH3COOCH2CH3 CH3CH2COOH A green solid was dissolved in water and the resulting solution divided into two portions. Sodium hydroxide solution was added to one of the portions and ammonia solution to the other. The results are summarised in the table below. Solution added Few drops of solution Excess solution Sodium hydroxide solution Green precipitate No effect Ammonia solution Green precipitate Dissolves to form a blue solution Which one of the following ions was present in the green solid? A B C D 8 Which one of the following is the colour of chrome alum crystals? A B C D 5622 3+ Cr Cu2+ Fe2+ Ni2+ Black Green Orange Violet 4 [Turn over 9 25.0 cm3 of hydrogen peroxide solution were added to excess acidified potassium iodide solution and the resulting solution made up to 500 cm3. 25.0 cm3 of the diluted solution reacted with 36.4 cm3 of sodium thiosulphate solution of concentration 0.10 mol dm 3. Which one of the following is the concentration of the undiluted hydrogen peroxide? A B C D 0.07 mol dm 3 0.15 mol dm 3 1.46 mol dm 3 2.91 mol dm 3 10 Which one of the following pairs of monomers will not combine to form a polymer? A B C D 5622 HOOC(CH2)4COOH and H2N(CH2)6NH2 H2N(CH2)6NH2 and H2N(CH2)6NH2 CH2CH2 and CH2CH2 HOOC(CH2)4COOH and HO(CH2)2OH 5 [Turn over Section B Examiner Only Marks Remark Answer all seven questions in this section 11 (a) Complete the table below by giving the name of the indicator and the colour change at the end point. Titration Colour change Indicator from to Edta added to magnesium ions Thiosulphate ions added to iodine [6] (b) Some iron tablets, used to treat anaemia, contain iron(II) fumarate (FeC4H2O4). Five of these iron tablets were dissolved in dilute sulphuric acid and the solution made up to 250 cm3 with distilled water. On titration 25.0 cm3 of this solution reacted with 18.7 cm3 of 0.01 mol dm 3 acidified potassium manganate(VII) solution. (i) Write the equation for the reaction of iron(II) ions with acidified manganate(VII) ions. __________________________________________________ [2] (ii) What is the colour change at the end point of the titration? From _________________ to __________________ [2] (iii) Calculate the mass of iron(II) fumarate in each tablet. ____________________________________________________ ____________________________________________________ ____________________________________________________ ____________________________________________________ __________________________________________________ [4] 5622 6 [Turn over 12 (a) Polythene is a typical addition polymer. Examiner Only Marks Remark (i) State the conditions necessary for the formation of HD polythene. Temperature: ________________________________________ Pressure: ___________________________________________ Catalyst: __________________________________________ [3] (ii) Making reference to their structures, explain the difference in flexibility between HD and LD polythene. ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (b) Polyethylene terephthalate is a polyester. (i) Draw the repeating unit for polyethylene terephthalate. [2] (ii) Give one use for polyethylene terephthalate. _________________________________________________ [1] 5622 7 [Turn over 13 Transition metals form complex ions with ligands. Examiner Only Marks Remark (a) Explain what is meant by the term polydentate ligand. _______________________________________________________ _____________________________________________________ [2] (b) The complex below is formed when dimethylglyoxime is added to a solution of hydrated nickel(II) ions. H 3C O C H CH3 O N N C N C Ni2+ C H 3C N O H CH3 O (i) What is the co-ordination number of the nickel(II) ion? _________________________________________________ [1] (ii) Suggest the shape around the central nickel(II) ion. _________________________________________________ [1] (iii) What type of bonds in the complex are represented by each of the following? ________________________________________________ ----- ________________________________________________ ______________________________________________ [3] 5622 8 [Turn over (c) Explain in terms of entropy why dimethylglyoxime displaces the water ligands in the hydrated nickel(II) ion to form the nickel(II) dimethylglyoxime complex. Examiner Only Marks Remark _______________________________________________________ _______________________________________________________ _____________________________________________________ [2] 5622 9 [Turn over 14 The explosive trinitrotoluene (TNT) is prepared by the nitration of methylbenzene (toluene). CH3 Examiner Only Marks Remark CH3 NO2 NO2 NO2 Toluene TNT (a) Suggest a systematic name for TNT. _____________________________________________________ [1] (b) TNT burns to form a mixture of carbon dioxide, nitrogen and water. Write an equation for the complete combustion of TNT. _____________________________________________________ [2] (c) TNT is prepared from toluene by using the same nitrating mixture as is used to nitrate benzene. (i) Name the acids present in the nitrating mixture. _________________________________________________ [2] (ii) Write an equation for the formation of the nitrating species. _________________________________________________ [2] (iii) What name is given to the nitrating species? _________________________________________________ [1] 5622 10 [Turn over (d) The mechanism for nitrating toluene is similar to that for nitrating benzene. Examiner Only Marks Remark (i) What name is given to this mechanism? _________________________________________________ [2] (ii) Draw the mechanism for the mononitration of toluene. [2] (e) 4-nitrotoluene can be converted to toluidine. CH3 NH2 Toluidine (i) Name the reagents which could be used to convert 4-nitrotoluene to toluidine. ____________________________________________________ __________________________________________________ [2] (ii) A salt of toluidine is formed during the reduction. How can toluidine be liberated from this salt? __________________________________________________ [1] 5622 11 [Turn over (f) Toluidine is used in the manufacture of dyes. The first step in the process is to convert the toluidine to its diazonium ion using nitrous acid. Examiner Only Marks Remark (i) Write an equation for the formation of nitrous acid from sodium nitrite. __________________________________________________ [1] (ii) What conditions are necessary for the reaction between toluidine and nitrous acid to form the diazonium ion? __________________________________________________ [1] (iii) Write an equation for the conversion of toluidine to its diazonium ion. __________________________________________________ [2] (g) One dye is made by reacting the toluidine diazonium ion with phenol. (i) What name is given to this type of reaction? __________________________________________________ [1] (ii) Draw the structure of the dye formed. [2] (iii) Explain why this dye is coloured. ____________________________________________________ ____________________________________________________ ____________________________________________________ _________________________________________________ [3] 5622 12 [Turn over BLANK PAGE (Questions continue overleaf) 5622 13 [Turn over 15 Vanadium and chromium are typical transition metals. Examiner Only Marks Remark (a) Explain, in terms of electronic structure, what is meant by a transition metal. _______________________________________________________ _____________________________________________________ [1] (b) Vanadium(V) oxide acts as a heterogeneous catalyst in the conversion of sulphur dioxide to sulphur trioxide in the manufacture of sulphuric acid. (i) Write the equation for the conversion of sulphur dioxide to sulphur trioxide. _________________________________________________ [1] (ii) What is meant by a heterogeneous catalyst? _________________________________________________ [1] (iii) Explain, in terms of chemisorption, how vanadium(V) oxide acts as a catalyst in this reaction. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [3] 5622 14 [Turn over (c) An acidified solution of ammonium vanadate(V) undergoes a series of reductions when it is stirred with zinc. Examiner Only Marks Remark (i) Complete the table below, giving the colour of VO2+(aq) and V3+(aq) formed at the different stages of the reduction. Ion Colour + VO2(aq) Yellow VO2+(aq) V3+(aq) V2+(aq) Violet [2] (ii) Chromium will also reduce ammonium vanadate(V). 3+ Cr (aq) + 3e + VO2(aq) + 2H+(aq) + e Cr(s) E /V 0.74 VO2+(aq) + H2O(l) +1.00 Write an equation for the reaction between chromium and + VO2(aq) ions and calculate the e.m.f. of the reaction. ___________________________________________________ e.m.f. ____________________________________________ [3] 5622 15 [Turn over (d) Potassium chromate(VI), K2CrO4 can be prepared by oxidising a solution of chromium(III) ions. Examiner Only Marks Remark (i) Name a suitable oxidising agent. _________________________________________________ [1] (ii) Give the colour change on oxidising the chromium(III) ions to chromate(VI) ions. from: _______________________________________________ to: _______________________________________________ [2] (iii) Chromate(VI) and dichromate ions are involved in the following equilibrium: 2CrO42 (aq) + 2H+(aq) Cr2O72 (aq) + H2O(l) State and explain the colour change when sodium hydroxide solution is added to this equilibrium. ___________________________________________________ ___________________________________________________ _________________________________________________ [3] 5622 16 [Turn over 16 The burning sensation felt when eating chilli peppers is caused by capsaicin. Examiner Only Marks Remark H HO CH3 H 3C CH2 N O CH2 C CH2 CH2 CH CH CH2 CH CH3 O Capsaicin (a) Capsaicin is used in pepper sprays at a concentration of 5% by mass per volume (5 g in 100 cm3). (i) What is the molecular formula of capsaicin? _________________________________________________ [1] (ii) Calculate the concentration of capsaicin in mol dm 3 of the pepper spray. ___________________________________________________ ___________________________________________________ _________________________________________________ [3] (b) A sample of capsaicin extracted from chilli peppers will contain a large number of organic impurities. Describe how you would use two-way paper chromatography to show that the sample contained capsaicin. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [4] Quality of written communication 5622 [2] 17 [Turn over 17 Proteins are formed from amino acids. Examiner Only Marks Remark (a) (i) Describe the primary, secondary and tertiary structure of proteins. Primary: ____________________________________________ _________________________________________________ [1] Secondary: __________________________________________ _________________________________________________ [2] Tertiary: ____________________________________________ _________________________________________________ [2] (ii) Explain why some proteins can act as enzymes. ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (iii) Explain why the efficiency of most enzymes is lowered at 60 C. ___________________________________________________ _________________________________________________ [2] (b) Aspartic acid and asparagine are amino acids. NH2 NH2 HOOC C COOH C H2NOC H H Aspartic acid COOH Asparagine (i) Suggest how aspartic acid could be converted to asparagine. _________________________________________________ [1] 5622 18 [Turn over (ii) Write an equation for the reaction between aspartic acid and asparagine to form a dipeptide. Examiner Only Marks Remark _________________________________________________ [2] (iii) Amino acids dissolve in water to form a dipolar ion (zwitterion). Draw the structure of the dipolar ion formed by asparagine. [1] (iv) Complete the following flow diagram to show the structure of the organic product formed. SOCl2 NH2 HCl H2NOC C COOH Na2CO3 H C2H5OH [4] 5622 19 [Turn over 5622

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Additional Info : Gce Chemistry June 2010 Assessment Unit A2 1 Analytical, Transition Metals and Further Organic Chemistry
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