14.1 Born Haber Cycle MgCl2 [PDF]

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Born-Haber Cycles



magnesium chloride



Mg2+(g) + 2e- + 2Cl enthalpy H



H



bond energy of chlorine



Mg2+(g) H



+



2e-



+ Cl2



(g)



(g)



2 x H Mg2+



first electron affinity (g)



+ 2Cl-



(g)



second ionisation energy



Mg+(g) + e- + Cl2 (g)



H



first ionisation energy



Mg



(g)



+ Cl2



(g)



H atomisation Mg (s) + Cl2 H



formation



H lattice association



(g)



MgCl2



(s)



1



Born-Haber Cycles



magnesium chloride



Mg2+(g) + 2e- + 2Cl enthalpy H



H



bond energy of chlorine



Mg2+(g) H



+



2e-



+ Cl2



(g)



(g)



2 x H Mg2+



first electron affinity (g)



+ 2Cl-



(g)



second ionisation energy



Mg+(g) + e- + Cl2 (g)



H



first ionisation energy



Mg



(g)



+ Cl2



(g)



H atomisation Mg (s) + Cl2 H



formation



H lattice association



(g)



MgCl2



(s)



2



Apply Hess’s Law to calculate ∆HLattice Energy for MgCl2 setting out the values in a methodical manner: 1



=



2



+



3



+



4



+ 5 +



6



+



7



-641 = +148 + 738 + 1451 + 242 + (2x-364) + ∆HLE



-641 = + 1851 + ∆HLE ∆HLE



= - 1851 - 641 = - 2492 kJ mol-1 3