Transcript MgCl2 Born Haber Cycle

Born-Haber Cycles
magnesium chloride
Mg2+(g) + 2e- + 2Cl (g)
enthalpy H
H
bond energy of chlorine
Mg2+(g)
(g)
H
+
2e-
+ Cl2
2 x H
first electron affinity
Mg2+ (g) + 2Cl- (g)
second ionisation energy
Mg+(g) + e- + Cl2 (g)
H
first ionisation energy
H
Mg (g) + Cl2 (g)
lattice
H atomisation
Mg (s)
Cl
(g)
(s) ++ Cl
2 2(g)
H
formation
MgCl2
(s)
1
Born-Haber Cycles
magnesium chloride
Mg2+(g) + 2e- + 2Cl (g)
enthalpy H
H
bond energy of chlorine
Mg2+(g)
H
+
2e-
+ Cl2 (g)
2 x H
first electron affinity
Mg2+ (g) + 2Cl- (g)
second ionisation energy
Mg+(g) + e- + Cl2 (g)
H
first ionisation energy
H
Mg (g) + Cl2 (g)
lattice
H atomisation
Mg (s) + Cl2 (g)
H
formation
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