AQA Jan 2012 Paper 5 Q1

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section a answer all questions in the spaces provided do not write outside the box this question is about magnesium oxide use data from the table below where appropriate to answer the following questions first electron affinity of oxygen formation of o g from o g second electron affinity of oxygen formation of o g from o g atomisation enthalpy of oxygen h kj mol a define the term enthalpy of lattice dissociation marks b in terms of the forces acting on particles suggest one reason why the first electron affinity of oxygen is an exothermic process mark extra space wmp jan chem do not write outside the box c complete the born haber cycle for magnesium oxide by drawing the missing energy levels symbols and arrows the standard enthalpy change values are given in kj mol mg g o g e mg g o g e mg g o g mg s o g mgo s marks d use your born haber cycle from part c to calculate a value for the enthalpy of lattice dissociation for magnesium oxide marks question continues on the next page turn over wmp jan chem do not write outside the box e the standard free energy change for the formation of magnesium oxide from magnesium and oxygen gf kj mol suggest one reason why a sample of magnesium appears to be stable in air at room temperature despite this negative value for gf mark extra space f use the value of gf given in part e and the value of hf calculate a value for the entropy change s when one mole of magnesium oxide is formed from magnesium and oxygen at k give the units of s from part c to marks extra space g in terms of the reactants and products and their physical states account for the sign of the entropy change that you calculated in part f marks wmp jan chem

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