IJC 2011 H2 CHEM P3 QN P

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2 PRELIM 2 © INNOVA 9647/03/2011 [Turn over Answer 4 out of 5 questions. 1 (a) (i) Manganese(IV) oxide, MnO 2 is the most common starting material for the production of compounds of manganese of other oxidation states. With reference to the Data Booklet , state which of the following ions would convert manganese(IV) oxide to manganese(II) sulfate in an acidic solution. P b 4+(aq) / Pb2+(aq) E = +1.69V C o 3+(aq) / Co2+(aq) E = +1.82V F e 3+(aq) / Fe2+(aq) E = +0.77V (ii) Calculate the E cell value to prove that the reaction between MnO 2 and the ion that you have chosen in a(i) is feasible and write a balanced equation for the reaction. (iii) What would be the colour of the final solution observed? [5] (b) (i) Write the full electronic configuration of Zn2+ and Mn2+. (ii) Explain why manganese forms compounds that are often coloured whereas compounds of zinc are usually white. [5] (c) MnO 2 undergoes the following reaction as shown in the schematic diagram below: Step I: Oxidation of MnO 2 in molten KOH with oxygen from the air produces a green compound, A. Step II: Reaction of A with dilute acid produced 0.174 g of MnO 2 and a purple solution of compound B was observed. A solution of compound B is just decolourised by 40.0 cm3 of 0.500 mol dm-3 iron(II) sulphate. (i) B contains potassium, manganese and oxygen only. Suggest the chemical formula of compound B that causes the solution to appear purple. (ii) Calculate the number of moles of MnO2 produced in step II. (iii) Calculate the number of moles of compound B produced in step II, given that compound B and iron(II) sulphate reacted in a 1:5 mole ratio. (iv) With reference to step II of the above reaction scheme, let the oxidation number of manganese in A be n, i.e. Mn n+. Using your answer to c(ii) and c(iii), write an expression in n to show (I) the no. of moles of electrons gained by Mn n+ when Mnn+ is reduced to MnO2 (II) the no. of moles of electrons lost by Mnn+ when Mnn+ is oxidised to B (v) Hence, using your answer to c(iv), calculate the oxidation number of manganese in compound A. [5]

3 PRELIM 2 © INNOVA 9647/03/2011 [Turn over (d) (i) Cl2 reacts with benzene in the presence of a suitable catalyst. Describe the mechanism and suggest the product obtained. (ii) The reaction in d(i) can only take place under anhydrous conditions. Suggest a reason to explain why it is so. [5] [Total: 20]

4 PRELIM 2 © INNOVA 9647/03/2011 [Turn over 2 (a) This question is related to the chemistry of carbonyl compounds to form nitrogen- containing compounds. Bupropion is an anti-depressant that was subsequently found to be useful as a smoking cessation aid. It reduces the severity of nicotine cravings and withdrawal symptoms. It can be synthesised from compound C, from which many derivatives of bupropion can also be synthesised. (i) Suggest the type of reaction occurring in step I. (ii) Name the type of reaction in step III and state the reagent(s) and condition(s) involved. (iii) Given that bupropion is basic, without using fractional distillation, suggest a reagent and a suitable separation technique that you will use to isolate the product bupropion from the reaction mixture. Describe what you will observe in the process. (iv) Suggest the reagents and conditions required in step IV and state and describe the mechanism of this step. (v) Based on your answer in a(iv), suggest and explain whether the product of step IV is optically active or optically inactive. [12]

5 PRELIM 2 © INNOVA 9647/03/2011 [Turn over (b) When two colourless gases dinitrogen tetraoxide and nitrogen monoxide are mixed at room temperature, the two gases react slowly to form the blue compound dinitrogen trioxide according to the following equilibrium. N2O4(g) + 2NO(g) 2N 2O3(g) ∆H negative blue A gas syringe is filled with the colourless gases and sealed. When the gases are compressed, the blue colour becomes more intense. When the system is warmed, the blue colour fades. (i) Use Le Chatelier’s Principle to explain the above observations. (ii) At low temperatures, N 2O3 exists as a deep blue liquid. Using your knowledge of the chemistry of P 4O6, state the acid-base nature of N 2O3 and write an equation with state symbols to illustrate your answer. [5] (c) (i) A large portion of the copper produced in the world is obtained by the smelting of chalcopyrite. It is an iron-containing mineral with the molecular formula of CuFeS 2. Smelting of chalcopyrite can be represented by the following equation: 3CuFeS2 + 8O2 3Cu + FeO + Fe 2O3 + 6SO2 Calculate the volume of sulfur dioxide gas released into the atmosphere at r.t.p. if 1 tonne of the rock sample is smelted. It is estimated that the rock contains 1.5% by mass of chalcopyrite. [1 tonne = 1000 kg] (ii) Why is it important to remove SO 2 from the products of smelting before release into the atmosphere? [3] [Total: 20]

6 PRELIM 2 © INNOVA 9647/03/2011 [Turn over 3 (a) Atenolol is a drug used mainly to prevent hypertension and coronary heart disease. Atenolol [Assume that the ether functional group is inert and does not undergo any reaction.] Draw the structural formula of the organic product formed when Atenolol is treated with the following reagents: (i) Hot aqueous hydrochloric acid (ii) Ethanoyl chloride [4] (b) Part of the reaction scheme for the formation of Atenolol involves the synthesis of the ether functional group via two possible routes: (i) Which route will give a greater yield of the product? Explain your reasoning. (ii) Another drug, Ketoprofen, commonly used in painkillers, has the stru