OCR A Jan 2012 Paper 2 Q5

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5 Sulfuric acid is made from sulfur, oxygen and water in a three-stage process. This can be represented by the following overall equation. 12 2S(s) + 3O2(g) + 2H2O(l) 2H2SO4(l) (a) Explain why the overall process to make sulfuric acid has an atom economy of 100%.[1] (b) A factory uses 51.4 tonnes of sulfur to manufacture 147 tonnes of H2SO4. What is the percentage yield of H2SO4? Give your answer to two significant figures. (1 tonne = 1106 g) percentage yield =% [3]OCR 2012<br />
 (c) One of the reactions involved in making sulfuric acid converts sulfur dioxide, SO2, into sulfur trioxide, SO3. 13 2SO2(g) + O2(g) 2SO3(g) H = 197 kJ mol1 This reaction can be carried out at 450 C and 3 atmospheres pressure in the presence of a V2O5 catalyst. Under these conditions the position of equilibrium is almost completely on the right-hand side. (i) A research chemist investigates this reaction. He uses a temperature of 450 C and 3 atmospheres pressure. The research chemist does not use the catalyst. Predict the changes, if any, on each of the following. position of equilibriumrate of backward reaction[2] (ii) The temperature of the reaction mixture is increased to 600 C. State and explain what will happen to the position of equilibrium.[1] (iii) The pressure of the reaction mixture is decreased to 2 atmospheres. State and explain what will happen to the position of equilibrium.[1]OCR 2012 Turn over<br />
 (d) Concentrated H2SO4 is used as an acid catalyst in the elimination of water from alcohols. 14 There are several alcohols that are structural isomers with the formula C5H11OH. When these alcohols are heated with H2SO4 they form alkenes. C5H11OH C5H10 + H2O (i) Pentan-1-ol is a structural isomer of C5H11OH that is a primary alcohol. Draw the structure of another structural isomer of C5H11OH that is a primary alcohol. (ii) Pentan-2-ol is a structural isomer of C5H11OH that is a secondary alcohol. Pentan-2-ol is heated with H2SO4. Three alkenes are formed, L, M and N. L and M are stereoisomers.N is a structural isomer of the stereoisomers L and M. Draw the structures for alkenes L, M and N. alkene L alkene M alkene N [1] [3]OCR 2012<br />
 (iii) One structural isomer of C5H11OH is an alcohol that cannot be oxidised by heating with acidified potassium dichromate(VI). 15 Draw the structure of this alcohol. [1] [Total: 13]OCR 2012 Turn over<br />

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