![9-030: Lattice Energy Calculation
Use the following information to calculate AHattice for MgCl2.
Mg(s) Mg(g)
Cl2(9) → 2Cl(9)
A H° = 148 kJ
%3D
A H° =
= 243 kJ
M9(g) Mg (g)+e¯
A H° = 738 kJ
Mg (g) Mg*(g)+e
2+
A H° =
= 1450 kJ
Clg) +e → Cl(9)
A H° = -349 kJ
Mg(s)+ Cl2(g) → M9CI2(s) A Hf° = -641.6 kJ
%3D
-2082 kJ/mol
Try to set up a Born-Haber cycle for the process of forming the compound.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc7221061-cab3-4d12-b574-9340e14d2678%2Fc728d1a6-ec2a-4ab3-b57b-7cc849157408%2Fr3cfmjk_processed.jpeg&w=3840&q=75)
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Solutions=
Let us calculate the lattice enthalpy of Magnesium chloride by the following steps given below:
1. Sublimation of Magnesium solid into gaseous state atom, sublimation enthalpy:
Mg(s)→Mg(g)
Δsub H° =148KJ/mol
2. The ionization of gaseous magnesium atom into an ion, ionization enthalpies:
Mg(g)→Mg1+(g)+1e-(g)
Δ1st lE H° = 738KJ/mol
Mg1+(g)→Mg2+(g)+1e−(g)
Δ2nd IEH° = 1451KJ/mol
3. The dissociation of chlorine molecule into gaseous atoms, bond dissociation enthalpy:
Cl2(g)→2Cl(g)
Δbond H° =2×122
= 244KJ/mol
4. The electrons gained by the chlorine atoms; electron gain enthalpy:
2Cl+2e−(g)→2Cl−
Δeg H° =2 ×−349
= -698KJ/mol
5. The enthalpy of formation of magnesium chloride is:
Mg2+(g)+2Cl−(g)→MgCl2
Δform H°= -641.8KJ/mol
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