AQA Jan 2011 Paper 5 Q2

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do not write outside the box the balance between enthalpy change and entropy change determines the feasibility of a reaction the table below contains enthalpy of formation and entropy data for some elements and compounds hf kj mol s j k mol n g o g no g c graphite c diamond a explain why the entropy value for the element nitrogen is much greater than the entropy value for the element carbon graphite marks b suggest the condition under which the element carbon diamond would have an entropy value of zero mark c write the equation that shows the relationship between g h and s for a reaction mark d state the requirement for a reaction to be feasible mark wmp jan chem do not write outside the box e consider the following reaction that can lead to the release of the pollutant no into the atmosphere n g o g no g use data from the table on page to calculate the minimum temperature above which this reaction is feasible marks f at temperatures below the value calculated in part e decomposition of no into its elements should be spontaneous however in car exhausts this decomposition reaction does not take place in the absence of a catalyst suggest why this spontaneous decomposition does not take place mark g a student had an idea to earn money by carrying out the following reaction c graphite c diamond use data from the table on page to calculate values for h and s for this reaction use these values to explain why this reaction is not feasible under standard pressure at any temperature h s explanation marks turn over wmp jan chem

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