AQA Jun 2015 Paper 2 Q5

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do not write outside the box a there are many uses of halogenated organic compounds despite environmental concerns bromotrifluoromethane is used in fire extinguishers in aircraft bromotrifluoromethane is formed when trifluoromethane reacts with bromine chf br cbrf hbr the reaction is a free radical substitution reaction similar to the reaction of methane with chlorine a i write an equation for each of the following steps in the mechanism for the reaction of chf with br initiation step marks first propagation step second propagation step a termination step a ii state one condition necessary for the initiation of this reaction mark wmp jun chem do not write outside the box b bromine containing and chlorine containing organic compounds may have a role in the decomposition of ozone in the upper atmosphere b i draw an appropriate displayed formula in the space provided to complete the following equation to show how cbrf may produce bromine atoms in the upper atmosphere mark cbrf br b ii in the upper atmosphere it is more likely for cbrf to produce bromine atoms than it is for cclf to produce chlorine atoms suggest one reason for this mark question continues on the next page turn over wmp jun chem do not write outside the box b iii bromine atoms have a similar role to chlorine atoms in the decomposition of ozone the overall equation for the decomposition of ozone is o o write two equations to show how bromine atoms br act as a catalyst in the decomposition of ozone explain how these two decomposition equations show that bromine atoms behave as a catalyst marks equation equation explanation wmp jun chem

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