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GCE JAN 2009 : (A2 1) Further Organic, Physical and Inorganic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education January 2009 Chemistry assessing Module 4: Further Organic, Physical and Inorganic Chemistry A2C11 Assessment Unit A2 1 [A2C11] FRIDAY 9 JANUARY, 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 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. For Examiner s use only Question Number INFORMATION FOR CANDIDATES Marks Section A The total mark for this paper is 90. Quality of written communication will be assessed in question 13(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. 1 10 4272 Total Marks Section B 11 12 13 14 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 rate of decomposition of ethanal at 500 C is given by the equation below: rate = k [ethanal]2 What are the units of k? A B C D 2 An organic compound, X, gives an orange crystalline product with 2,4-dinitrophenylhydrazine, but does not give a precipitate on heating with Fehling's solution. Which one of the following formulae is that of X? A B C D 3 HCHO C6H5CH2CHO CH3COCH3 CH3CH2CO2H A gaseous mixture of 1.0 g of hydrogen and 2.8 g of nitrogen has a total pressure of 660.0 kPa at a particular temperature. What is the partial pressure of hydrogen in the mixture? A B C D 4272 s 1 mol dm 3 s 1 mol 1 dm3 s 1 mol2 dm 6 s 1 110.0 kPa 220.0 kPa 440.0 kPa 550.0 kPa 2 [Turn over 4 Which one of the following oxides has a molecular structure as distinct from a giant structure? A B C D 5 How many moles of ethanoyl chloride would react with one mole of glucose, assuming that glucose can be represented by the formula CH2OH(CHOH)4CHO? A B C D 6 2-methylbutan-1-ol 2-methylbutan-2-ol 3-methylbutan-1-ol 3-methylbutan-2-ol An aqueous solution containing 1 mol of S2O32 ions reduces 4 mol of Cl2 molecules. Which one of the following is a product of the reaction? Note that water is a reactant. A B C D 4272 1 4 5 6 Which one of the following alcohols, all with molecular formula C5H12O, could not be produced by the reduction of an aldehyde or a ketone? A B C D 7 Al2O3 Cl2O7 Na2O SiO2 S SO2 SO32 SO42 3 [Turn over 8 A 0.20 g sample of a monobasic acid requires 8.0 cm3 of 0.40 mol dm 3 sodium hydroxide solution for complete reaction. Which one of the following is the relative molecular mass of the acid? A B C D 9 62.5 250.0 625.0 640.0 Pain is often felt when a piece of aluminium foil touches an amalgam filling in a tooth because an electrical current briefly flows. The amalgam contains tin. The standard electrode potentials are: Al3+ + 3e Al 1.66 V Sn2+ + 2e Sn 0.13 V Which one of the following statements concerning the resulting cell is correct? A B C D Aluminium ions are produced from the foil. The aluminium foil acts as the positive electrode. The e.m.f. of the cell is + 1.79 V. Tin ions are discharged into the saliva in the mouth. 10 An aqueous solution of ammonium chloride has a pH less then 7 because A B C D 4272 the ammonium ions donate protons to water molecules. the chloride ions combine with hydrogen ions to form hydrochloric acid. aqueous ammonium chloride is unstable and evolves ammonia gas leaving hydrochloric acid. the ammonium ions combine with hydroxide ions to form ammonium hydroxide leaving an excess of hydrogen ions. 4 [Turn over Section B Examiner Only Marks Remark Answer all four questions in the spaces provided. 11 The extent of the manufacture of sulphuric acid was a major indicator of the wealth of a nation. Today the consumption of oil or ferrous metals shows the economic development of industrial nations. Sulphuric acid, however, remains a chemical that the developed world still needs. (a) Explain the use of sulphuric acid in the agricultural industry. _________________________________________________________ _______________________________________________________ [2] (b) In the Contact process, sulphuric acid is manufactured from sulphur. Write three equations for the reactions occurring in this process. _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (c) Sulphur dioxide is prevented from escaping to the atmosphere during the process. Explain the precautions taken against the emission of sulphur dioxide and why they are needed. _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] 4272 5 [Turn over (d) Concentrated sulphuric acid reacts with copper metal. Examiner Only Marks Remark (i) Write an equation for the reaction ___________________________________________________ [1] (ii) Using oxidation numbers, explain why the reaction can be regarded as a redox reaction. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (e) The strength of an acid is related to the value of the oxidation number of the central atom in the acid. Explain, using this theory, whether sulphuric acid is stronger than thiosulphurous acid, H2S2O3. _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (f) A solution of sulphuric acid reacts with aqueous barium chloride. (i) Write an ionic equation for the reaction including state symbols. ___________________________________________________ [2] (ii) Describe what would be observed. _____________________________________________________ ___________________________________________________ [2] 4272 6 [Turn over (iii) Calculate the mass, in milligrams, of barium sulphate produced if 19.0 cm3 of 0.01 M sulphuric acid is added to 50 cm3 of a barium chloride solution with a concentration of 0.16 g dm 3. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [4] 4272 7 [Turn over 12 The invention of the pH scale is credited to the Danish biochemist S renson whilst working for Carlsberg on problems connected with the brewing of lager. Control of acidity was essential. Continually referring to the hydrogen ion concentration was tedious and he suggested the use of a pH scale as a more convenient measure of acidity. Examiner Only Marks Remark (a) The acidity in lager is caused by weak acids. Explain the term weak acid. _________________________________________________________ _______________________________________________________ [2] (b) When exposed to air, lagers and beers turn sour and the pH decreases. Suggest what causes this to happen. _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (c) A lager investigated by S renson had a hydrogen ion concentration of 5.10 10 8 mol cm 3 . Calculate the pH of this lager. _________________________________________________________ _______________________________________________________ [2] (d) pH values depend on the temperature at which they are measured because of the variation of the ionic product of water with temperature, as shown in the table below. Temperature/K Kw/mol2 dm 6 298 1.0 10 14 333 5.6 10 14 (i) Write an equation for the ionic product of water. ___________________________________________________ [1] (ii) Deduce whether the dissociation of water is an exothermic or endothermic process. Explain your reasoning. _____________________________________________________ ___________________________________________________ [2] 4272 8 [Turn over (e) Lagers and beers are produced by the fermentation of sugars and starches. Examiner Only Marks Remark (i) Name a monosaccharide sugar. ___________________________________________________ [1] (ii) Name the two types of polymer in starch. ___________________________________________________ [1] (f) The carbon dioxide produced in the brewing process may be collected by dissolving in water under pressure. The carbonic acid and the hydrogencarbonate ion produced are involved in an equilibrium reaction which acts as a buffer system. (i) Using an equilibrium equation, explain the result of adding separately an acid and an alkali to this buffer system. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) Calculate how many grams of sodium ethanoate must be added to 500 cm3 of 0.01 mol dm 3 ethanoic acid to produce a buffer solution of pH 5.8. Ka(CH3COOH) = 1.86 10 5 mol dm 3 _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [4] 4272 9 [Turn over 13 The partially completed Born Haber cycle for magnesium chloride is shown below. Examiner Only Marks Remark Mg2+(g) + Cl2(g) + 2e Mg+(g) + Cl2(g) + e Mg(g) + Cl2(g) Mg(s) + Cl2(g) MgCl2(s) (a) (i) Complete the two empty boxes. [2] (ii) Using the data below, calculate the lattice enthalpy for magnesium chloride. First ionisation energy of magnesium Second ionisation energy of magnesium Enthalpy of atomisation of magnesium Enthalpy change of formation of magnesium chloride Enthalpy of atomisation of chlorine Electron affinity of chlorine kJ mol 1 +738 +1451 +148 641 +121 348 _____________________________________________________ ___________________________________________________ [2] (iii) Explain, in terms of electrostatic forces and using magnesium chloride as an example, what is meant by the term lattice enthalpy. _____________________________________________________ ___________________________________________________ [2] 4272 10 [Turn over (iv) The lattice enthalpies of the magnesium halides calculated using the Born Haber cycle are shown below. Magnesium halide +2913 Magnesium bromide +2097 Magnesium iodide Remark Theoretical lattice enthalpy Magnesium fluoride Examiner Only Marks +1944 Suggest, using the enthalpy values in the Born Haber cycle, why the lattice enthalpies decrease. _____________________________________________________ ___________________________________________________ [2] (b) Magnesium chloride has ionic bonding as described in the Born Haber cycle. Show the formation of magnesium chloride from magnesium and chlorine atoms using dot and cross diagrams. [3] (c) Magnesium iodide reacts with both sulphuric acid and phosphoric acid. Compare and contrast these reactions giving experimental observations and theoretical explanations. Equations are not required. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [5] Quality of written communication 4272 [2] 11 [Turn over 14 Natural fats and oils are generally a mixture of various esters of glycerol containing more than one kind of fatty acid, which may be saturated or unsaturated. A table of some oils and fats is shown below. Examiner Only Marks Remark Percentage of total fatty acids by mass Oil/fat saturated monounsaturated polyunsaturated 6 1 Sunflower oil 11 19 70 Lard 44 46 10 Peanut oil 21 49 30 Coconut oil 93 (a) (i) Explain why it is important to have a mixture of saturated and unsaturated oils/fats in a balanced diet. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) Suggest the meaning of the term monounsaturated fatty acid. _____________________________________________________ ___________________________________________________ [2] (iii) Name an unsaturated fatty acid found in some natural fats and oils. ___________________________________________________ [1] (iv) Give the systematic name for glycerol, which reacts with fatty acids to form oils and fats. ___________________________________________________ [2] 4272 12 [Turn over (b) A sample containing 1.20 g of oil, containing a mixture of unsaturated triglycerides is saponified by 3.30 10 3 mol potassium hydroxide. A second sample, also containing 1.20 g of the same oil, is found to react completely with 5.38 10 3 mol hydrogen in the presence of a catalyst. (i) Calculate the number of moles of the triglycerides in the oil. _____________________________________________________ ___________________________________________________ [1] (ii) Calculate the average relative molecular mass of the triglycerides in the oil. ___________________________________________________ [1] (iii) Calculate the average number of carbon carbon double bonds per fatty acid molecule in the original triglycerides. ___________________________________________________ [1] (iv) Name the catalyst used in the hydrogenation. ___________________________________________________ [1] (v) Suggest how you could show that the hydrogenated glyceride contains no carbon carbon double bonds. _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] THIS IS THE END OF THE QUESTION PAPER 4272 13 Examiner Only Marks Remark 935-068-1 [Turn over

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Additional Info : Gce Chemistry January 2009 Assessment Unit A2 1 Module 4: Further Organic, Physical and Inorganic Chemistry
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