AQA Jun 2011 Paper 5 Q3

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do not write outside the box ammonia can be manufactured by the haber process the equation for the reaction that occurs is shown below a the table below contains some bond enthalpy data n g h g nh g mean bond enthalpy kj mol n n h h n h a i use data from the table to calculate a value for the enthalpy of formation for one mole of ammonia marks a ii a more accurate value for the enthalpy of formation of ammonia is kj mol suggest why your answer to part a i is different from this value mark wmp jun chem do not write outside the box b the table below contains some entropy data h g n g nh g s j k mol use these data to calculate a value for the entropy change with units for the formation of one mole of ammonia from its elements marks c the synthesis of ammonia is usually carried out at about k c i use the h value of kj mol and your answer from part b to calculate a value for g with units for the synthesis at this temperature if you have been unable to obtain an answer to part b you may assume that the entropy change is j k mol this is not the correct answer marks c ii use the value of g that you have obtained to comment on the feasibility of the reaction at k mark turn over wmp jun chem

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