AQA Jun 2013 Paper 5 Q3

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a figure shows how the entropy of a molecular substance x varies with temperature do not write outside the box figure l t k l o s j k mol a i explain in terms of molecules why the entropy is zero when the temperature is zero kelvin marks extra space a ii explain in terms of molecules why the first part of the graph in figure is a line that slopes up from the origin marks extra space wmp jun chem do not write outside the box a iii on figure mark on the appropriate axis the boiling point tb of substance x mark a iv in terms of the behaviour of molecules explain why l is longer than l in figure marks extra space question continues on the next page turn over wmp jun chem do not write outside the box b figure shows how the free energy change for a particular gas phase reaction varies with temperature figure g kj mol t k b i explain with the aid of a thermodynamic equation why this line obeys the mathematical equation for a straight line y mx c marks b ii explain why the magnitude of g decreases as t increases in this reaction mark b iii state what you can deduce about the feasibility of this reaction at temperatures lower than k mark wmp jun chem do not write outside the box c the following reaction becomes feasible at temperatures above k h o g h g o g the entropies of the species involved are shown in the following table s j k mol h o g h g o g c i calculate the entropy change s for this reaction mark c ii calculate a value with units for the enthalpy change for this reaction at k if you have been unable to answer part c i you may assume that the value of the entropy change is j k mol this is not the correct value marks turn over wmp jun chem

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