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GCE MAY 2008 : (A2 1) Further Organic, Physical and Inorganic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2008 Chemistry assessing Module 4: Further Organic, Physical and Inorganic Chemistry A2C11 Assessment Unit A2 1 [A2C11] THURSDAY 22 MAY, 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 fifteen 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 five 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 INFORMATION FOR CANDIDATES The total mark for this paper is 90. Quality of written communication will be assessed in question 14(a)(iv). 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. A2C1S8 3606 1 10 Section B 11 12 13 14 15 Total Marks 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 The slowest stage in the production of sulphuric acid involves the conversion of sulphur dioxide to sulphur trioxide. 2SO2(g) + O2(g) 2SO3(g) H = 197 kJ What effect does adding a catalyst have on the rates of the forward and reverse reactions and the equilibrium constant? rate of forward reaction rate of reverse reaction equilibrium constant A increases increases increases increases C increases decreases no effect D increases increases no effect The partition coefficient of an organic compound X between ether and water is 20. An aqueous solution containing 5.00 g of X in 250 cm3 of water was shaken with 100 cm3 of ether. What mass of X remained in the aqueous layer following the extraction? A B C D 3 decreases B 2 decreases 0.56 g 1.67 g 3.33 g 4.44 g For the reaction H2SO4 + HNO3 HSO4 + H2NO3+ HNO3 is the A B C D A2C1S8 conjugate acid of H2NO3+ conjugate acid of HSO4 conjugate base of H2NO3+ conjugate base of HSO4 3606 2 [Turn over 4 Which one of the following reactions in the Born Haber cycle for potassium iodide is exothermic? A B C D 5 KI(s) K+(g) + I (g) K(g) K+(g) + e I2(g) 2I(g) I(g) + e I (g) The pharmaceutical drug antifebrin, CH3CONHC6H5, is made by the reaction of ethanoic anhydride with phenylamine. (CH3CO)2O + C6H5NH2 CH3CONHC6H5 + CH3COOH 6.0 g of ethanoic anhydride, (CH3CO)2O, reacted with 4.0 g of phenylamine, C6H5NH2, to produce 3.8 g of antifebrin. The percentage yield is A B C D 6 48.6% 63.3% 65.4% 95.0% In which one of the following reactions is no gas evolved? A B C D A2C1S8 copper metal with concentrated nitric acid concentrated sulphuric acid with solid potassium iodide thionyl chloride with ethanoic acid aqueous sodium sulphite with potassium manganate(VII) solution 3606 3 [Turn over 7 The mechanism for the reaction between propanone and iodine proceeds in a series of steps as follows: CH3COCH3 + H3O+ CH3C(OH)+CH3 + H2O slow CH3C(OH)+CH3 + H2O CH2 = C(OH)CH3 + H3O+ fast CH2 = C(OH)CH3 + I2 CH2ICOCH3 + HI fast The orders with respect to propanone, hydroxonium (H3O+) and iodine which support this would be: CH3COCH3 H3O+ I2 1 1 0 1 1 0 0 1 0 0 1 1 A B C D 8 Which one of the following equimolar salt solutions would have the highest pH? A B C D 9 ammonium chloride ammonium ethanoate sodium chloride sodium ethanoate Ammonia may be oxidised by mixing it with air and passing the mixture over a heated platinum rhodium catalyst. 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) Assuming air to be 20% oxygen, what volume of air is needed to react completely with 10.0 dm3 of ammonia at 20 C and 1 atmosphere pressure? A B C D A2C1S8 12.5 dm3 40.0 dm3 50.0 dm3 62.5 dm3 3606 4 [Turn over 10 Given the following half-equations E /V Br2(aq) + 2e 2Br (aq) O2(g) + 4H+(aq) + 4e 2H2O(l) S2O82 (aq) + 2e 2SO42 (aq) +1.07 +1.23 +2.01 which one of the following species could oxidise water to oxygen? A B C D A2C1S8 Br (aq) Br2(aq) SO42 (aq) S2O82 (aq) 3606 5 [Turn over Section B Examiner Only Marks Remark Answer all five questions in the spaces provided. 11 Glucose is a white crystalline solid which exhibits the reactions of an aliphatic aldehyde. Its structure can be represented as: CHO CHOH CHOH CHOH CHOH CH2OH (a) State what is observed when glucose is boiled with Fehling s solution. ______________________________________________________ [1] (b) Glucose is optically active. (i) Explain the meaning of the term optically active. _____________________________________________________ ___________________________________________________ [1] (ii) How many asymmetric centres are there in a glucose molecule? ___________________________________________________ [1] A2C1S8 3606 6 [Turn over (c) Draw the structure of the product formed between glucose and 2,4-dinitrophenylhydrazine, representing glucose as RCHO. Examiner Only Marks Remark [2] (d) Fermentation of glucose produces ethanol and carbon dioxide. The reaction is catalysed by the enzyme zymase found in yeast. (i) Write an equation for the fermentation of glucose. ___________________________________________________ [2] (ii) State what effect the enzyme has on the activation energy for this reaction. ___________________________________________________ [1] A2C1S8 3606 7 [Turn over 12 Nitrogen monoxide, NO, is a colourless gas which is formed in the reaction between moderately concentrated nitric acid and copper metal. In the presence of air it is immediately oxidised to the dioxide. Examiner Only Marks Remark (a) Write the equation for the formation of nitrogen monoxide from nitric acid and copper. ______________________________________________________ [2] (b) The oxidation of nitrogen monoxide is represented by the equation: 2NO(g) + O2(g) 2NO2(g) The kinetics of this reaction were studied and the following results recorded. Experiment Initial concentration of NO 10 3 mol dm 3 Initial concentration of O2 10 3 mol dm 3 Initial rate 10 4 mol dm 3 s 1 1 2 3 4 5 1 2 3 2 3 1 1 1 2 3 6 24 54 48 162 (i) Using these results, deduce the order of the reaction with respect to nitrogen monoxide and oxygen and write the overall rate equation. order with respect to NO _________________________________ order with respect to O2 __________________________________ rate equation ________________________________________ [3] (ii) On the axes below, sketch the shape of the graph expected in each case. [NO] rate time A2C1S8 3606 [NO] 8 [2] [Turn over (iii) Use the results for experiment 1 to determine the value of the rate constant and state its units. Examiner Only Marks Remark ______________________________________________________ ______________________________________________________ ___________________________________________________ [3] (c) Nitrogen dioxide, NO2, is a brown gas which dimerises to form colourless dinitrogen tetroxide, N2O4. The following equilibrium is established. N2O4(g) 2NO2(g) H = + 58 kJ (i) State and explain the effect of reducing the total pressure on the above equilibrium. ______________________________________________________ ______________________________________________________ ___________________________________________________ [2] (ii) A sealed flask containing pure dinitrogen tetroxide was heated to 80 C and equilibrium allowed to establish. At equilibrium, the total pressure was 125 kPa and the mole fraction of dinitrogen tetroxide was found to be 0.20. Calculate the value of Kp for this reaction, stating its units. ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ___________________________________________________ [4] (iii) State and explain the effect of increasing the temperature on the value of Kp. ______________________________________________________ ______________________________________________________ ___________________________________________________ [2] A2C1S8 3606 9 [Turn over (d) Nitrogen dioxide dissolves in water to form an acidic solution. Examiner Only Marks Remark 2NO2 + H2O HNO3 + HNO2 The nitrous acid decomposes to form more nitric acid. (i) Explain the relative strengths of nitrous and nitric acids. ______________________________________________________ ______________________________________________________ ___________________________________________________ [2] (ii) Given the half equations VO2+(aq) + 2H+(aq) +e V3+ + H2O(l) E = +0.34 V NO3 (aq) + 4H+(aq) + 3e NO(g) + 2H2O(l) VO2+(aq) + 2H+(aq) + e VO2+(aq) + H2O(l) E = +1.00 V E = +0.96 V deduce the equation for the reaction which occurs when nitric acid is added to a solution containing a mixture of V3+ and VO2+ ions. ___________________________________________________ [2] (iii) A text book notes that nitrous acid can act as both an oxidising agent and a reducing agent . With reference to oxidation number, explain this statement by referring to the reactions of the acid with acidified aqueous solutions of iron(II) sulphate and potassium manganate(VII). ______________________________________________________ ______________________________________________________ ______________________________________________________ ___________________________________________________ [4] A2C1S8 3606 10 [Turn over 13 Using only elements from the third period of the Periodic Table, answer the following questions. Examiner Only Marks Remark (a) (i) Write the formula of the metallic chloride which contains both covalent and coordinate (dative) bonds. ___________________________________________________ [1] (ii) Which element forms an oxide in which its oxidation state is +5? ___________________________________________________ [1] (iii) Name the element which forms an oxide with a giant covalent structure. ___________________________________________________ [1] (b) Aluminium oxide is amphoteric. (i) Explain the term amphoteric. ______________________________________________________ ___________________________________________________ [1] (ii) Write the equation for the reaction between aluminium oxide and sulphuric acid. ___________________________________________________ [2] A2C1S8 3606 11 [Turn over 14 Linoleic acid (octadeca-9,12-dienoic acid), is one of two essential fatty acids in our diet since our bodies are unable to synthesise it. Examiner Only Marks Remark CH3(CH2)4CH = CHCH2CH = CH(CH2)7COOH linoleic acid Deficiency can lead to scaly skin and hair loss. Glyceryl esters of the acid are plentiful in sunflower oil. (a) (i) The configuration at each double bond is cis. Draw the structure of linoleic acid. [1] (ii) Draw the structure of the oil formed when one molecule of glycerol reacts with three molecules of linoleic acid, representing the acid as C17H31COOH. [2] (iii) The iodine value for sunflower oil is typically in the range 125 145, while that of butter is 26 45. Explain these differences. ______________________________________________________ ___________________________________________________ [2] A2C1S8 3606 12 [Turn over (iv) Describe how the iodine value of a sample of sunflower oil may be determined. Examiner Only Marks Remark ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ___________________________________________________ [4] Quality of written communication [2] (b) Rancidity results from the oxidation of fats and oils in the absence of enzymes. This autoxidation may be slowed down by the addition of antioxidants such as citric acid which has the structure: CH2COOH HO C COOH CH2COOH (i) Write an equation to show the reaction of citric acid with excess sodium hydroxide solution. ___________________________________________________ [2] (ii) Titration of 25.0 cm3 of a citric acid solution required 17.5 cm3 of 0.1 M sodium hydroxide solution. Calculate the concentration of citric acid in g dm 3. ______________________________________________________ ______________________________________________________ ______________________________________________________ ___________________________________________________ [4] A2C1S8 3606 13 [Turn over 15 Aldehydes and ketones are responsible for many familiar smells. Benzaldehyde is used to make almond essence while heptan-2-one gives blue cheese its odour. H Examiner Only Marks Remark O C CH3COCH2CH2CH2CH2CH3 benzaldehyde C6H5CHO heptan-2-one (a) Fruits such as apricots contain amygdalin, C20H27O11N, which is hydrolysed by enzymes to form benzaldehyde, glucose and hydrogen cyanide. Write the equation for this reaction. ______________________________________________________ [2] (b) Benzaldehyde reacts with hydrogen cyanide to form benzaldehyde cyanohydrin. (i) Suggest the flow scheme for the mechanism of this reaction. [3] (ii) Name the mechanism of this reaction. ___________________________________________________ [2] A2C1S8 3606 14 [Turn over (c) Benzaldehyde may be oxidised using acidified potassium manganate(VII) to form benzoic acid, C6H5COOH. Benzoic acid is a weak acid with an acid dissociation constant, Ka, of 6.3 10 5 mol dm 3. Calculate the pH of a 0.001 M solution of benzoic acid. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] (d) (i) Explain the relative solubilities of propanone and heptan-2-one in water. ______________________________________________________ ______________________________________________________ ___________________________________________________ [2] (ii) Name the organic product formed when heptan-2-one reacts with lithal, LiAlH4. ___________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER A2C1S8 3606 15 [Turn over S 4/07 529-024-1 [Turn over

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Additional Info : Gce Chemistry May 2008 Assessment Unit A2 1 Module 4: Further Organic, Physical and Inorganic Chemistry
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