2 Born-Haber cycle

 

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1.8 Thermodynamics Page 2 - 3

Oxford Textbook Pages : 259 - 267

CGP Revision Guide Pages : 55 - 56

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Show Specification Ref : 3.1.8.1

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Question 1 / 5

AQA Jan 2010 Paper 1 Q1 section a answer all questions in the spaces provided pmt areas outside the box will not be scanned for marking ionisation energies provide evidence for the arrangement of electrons in atoms a complete the electron configuration of the mg ion s mark b i state the meaning of the term first ionisation energy marks b ii write an equation including state symbols to show the reaction that occurs when the second ionisation energy of magnesium is measured b mark iii explain why the second ionisation energy of magnesium is greater than the first ionisation energy of magnesium mark b iv use your understanding of electron arrangement to complete the table by suggesting a value for the third ionisation energy of magnesium ionisation energies of magnesium kjmol first second third fourth fifth mark wmp jan chem pmt areas outside the box will not be scanned for marking c state and explain the general trend in the first ionisation energies of the period elements sodium to chlorine trend explanation marks extra space d state how the element sulfur deviates from the general trend in first ionisation energies across period explain your answer how sulfur deviates from the trend explanation marks extra space e a general trend exists in the first ionisation energies of the period elements lithium to fluorine identify one element which deviates from this general trend mark turn over wmp jan chem
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Question 2 / 5

AQA Jan 2012 Paper 5 Q1 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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Question 3 / 5

AQA Jun 2010 Paper 5 Q1 section a answer all questions in the spaces provided do not write outside the box calcium fluoride occurs naturally as the mineral fluorite a very hard crystalline solid that is almost insoluble in water and is used as a gemstone tables and contain thermodynamic data table process ca s ca g ca g ca g e ca g ca g e f g f g f g e f g h kj mol table name of enthalpy change h kj mol enthalpy of lattice dissociation for calcium fluoride enthalpy of lattice dissociation for calcium chloride enthalpy of hydration for f ions enthalpy of hydration for cl ions enthalpy of hydration for ca ions a write an equation including state symbols for the process that occurs when the calcium fluoride lattice dissociates and for which the enthalpy change is equal to the lattice enthalpy mark wmp jun chem b i define the term standard enthalpy of formation do not write outside the box marks extra space b ii write an equation including state symbols for the process that has an enthalpy change equal to the standard enthalpy of formation of calcium fluoride mark b iii use data from the tables and to calculate the standard enthalpy of formation for calcium fluoride marks extra space question continues on the next page turn over wmp jun chem do not write outside the box c explain why the enthalpy of lattice dissociation for calcium fluoride is greater than that for calcium chloride marks d calcium chloride dissolves in water after a certain amount has dissolved a saturated solution is formed and the following equilibrium is established cacl s ca aq cl aq d i using data from table calculate the enthalpy change for this reaction marks d ii predict whether raising the temperature will increase decrease or have no effect on the amount of solid calcium chloride that can dissolve in a fixed mass of water explain your prediction if you have been unable to obtain an answer to part d i you may assume that the enthalpy change kj mol this is not the correct answer effect on amount of solid that can dissolve explanation marks wmp jun chem do not write outside the box e calcium fluoride crystals absorb ultra violet light some of the energy gained is given out as visible light the name of this process fluorescence comes from the name of the mineral fluorite use your knowledge of the equation e h to suggest what happens to the electrons in fluorite when ultra violet light is absorbed and when visible light is given out marks extra space turn over for the next question turn over wmp jun chem
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Question 4 / 5

AQA Jun 2012 Paper 5 Q3 do not write outside the box some thermodynamic data for fluorine and chlorine are shown in the table in the table x represents the halogen f or cl electronegativity electron affinity kj mol enthalpy of atomisation kj mol enthalpy of hydration of x g kj mol fluorine chlorine a explain the meaning of the term electron affinity marks b explain why the electronegativity of fluorine is greater than the electronegativity of chlorine marks extra space c explain why the hydration enthalpy of the fluoride ion is more negative than the hydration enthalpy of the chloride ion marks wmp jun chem do not write outside the box d the enthalpy of solution for silver fluoride in water is kj mol the hydration enthalpy for silver ions is kj mol d i use these data and data from the table to calculate a value for the lattice enthalpy of dissociation of silver fluoride marks d ii suggest why the entropy change for dissolving silver fluoride in water has a positive value mark d iii explain why the dissolving of silver fluoride in water is always a spontaneous process marks turn over wmp jun chem
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Question 5 / 5

AQA Jun 2014 Paper 5 Q1 section a answer all questions in the spaces provided do not write outside the box a write an equation for the process that has an enthalpy change equal to the electron affinity of chlorine mark b in terms of electrostatic forces suggest why the electron affinity of fluorine has a negative value marks c i complete the born haber cycle for silver fluoride by adding the missing species on the dotted lines marks ag g ag g ag g f g ag g ag s agf s wmp jun chem do not write outside the box c ii use the cycle in question c i and the data in table to calculate a value in kj mol for the bond enthalpy of the fluorine fluorine bond table enthalpy change enthalpy of atomisation for silver first ionisation energy for silver electron affinity for fluorine experimental enthalpy of lattice dissociation for silver fluoride enthalpy of formation for silver fluoride marks value kj mol question continues on the next page turn over wmp jun chem do not write outside the box d a theoretical value for enthalpy of lattice dissociation can be calculated using a perfect ionic model the theoretical enthalpy of lattice dissociation for silver fluoride is kj mol d i explain why the theoretical enthalpy of lattice dissociation for silver fluoride is different from the experimental value that can be calculated using a born haber cycle marks extra space d ii the theoretical enthalpy of lattice dissociation for silver chloride is kj mol explain why this value is less than the value for silver fluoride marks extra space wmp jun chem turn over for the next question do not write on this page answer in the spaces provided turn over wmp jun chem
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