OCR A Jun 2010 Paper 2 Q2

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2 Petrol and diesel are both complex mixtures of hydrocarbons used as fuels in transport. (a) Petrol contains some branched chain alkanes. The number of carbon atoms per molecule varies between five and nine. Name one branched chain alkane with between five and nine carbon atoms.[1] (b) When petrol burns in an internal combustion engine the exhaust gases contain CO2, CO, NO, N2, O2, H2O and unburnt hydrocarbons. (i) What effect does the absorption of infrared radiation have on the bonds in CO2 molecules in the atmosphere?[1] (ii) Why is CO present in the exhaust gases?[1] (iii) Both NO and CO are atmospheric pollutants. For each pollutant, describe one environmental problem. NOCO[2] (c) Most cars are fitted with a catalytic converter which catalyses the exothermic reaction between NO and CO to form two less harmful gases. (i) Name the two gases formed and write an equation for this reaction.[2]OCR 2010<br />
 (ii) NO and CO react very slowly without a catalyst. The catalyst in a catalytic converter increases the rate of reaction. Explain, using an enthalpy profile diagram and the Boltzmann distribution model, how the use of a catalyst increases the rate of reaction.[7]OCR 2010 Turn over<br />
 (d) Many lorries and some cars use diesel powered engines. Biodiesel is being developed as a substitute for diesel from crude oil. 10 Biodiesel is a methyl ester of a long chain carboxylic acid. The flow chart shows how it is produced. plants plant oil long chain carboxylic acids biodiesel Describe the benefits and disadvantages of changing from diesel to biodiesel.[3] [Total: 17]OCR 2010<br />

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