1. CI 4.6 – Born-Haber Cycle (C) JHUDSON 2005

2. For an ionic compound the lattice enthalpy is the enthalpy change when one mole of solid in its standard state is formed from its ions in the gaseous state. The lattice enthalpy cannot be measured directly and so we make use of other known enthalpies and link them together with an enthalpy cycle. This enthalpy cycle is the Born-Haber cycle. What do we mean by lattice enthalpy? -- - --  - - -       For an ionic compound the lattice enthalpy is the enthalpy change when one mole of solid in its standard state is formed from its ions in the gaseous state.

3. 1 Sublimation of Sodium Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) 0 +100 +200 +300 +400 +500 +600 +700 +800 kJmol -1 -400 -300 -200 -100 H = +107kJmol -1 θSθS Born-Haber Cycle for Sodium Chloride

4. 2 Bond Dissociation of Chlorine Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 H = +121kJmol -1 θDθD ½ Born-Haber Cycle for Sodium Chloride kJmol -1

5.  e-e- e-e- e-e- e-e- e-e- Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na + (g) + Cl(g) H = +502kJmol -1 θIθI Born-Haber Cycle for Sodium Chloride 3 First Ionisation of Sodium kJmol -1

6. 4 Electron Affinity of Chlorine e-e- Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na + (g) + Cl(g) Na + (g) + Cl - (g ) H = -355kJmol -1 θEθE Born-Haber Cycle for Sodium Chloride kJmol -1 -

7. Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 NaCl(s) Born-Haber Cycle for Sodium Chloride H = -411kJmol -1 θFθF Na + (g) + Cl(g) kJmol -1 -- - --     5 Formation of Sodium Chloride Na + (g) + Cl - (g)

8. Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 Na (s) + 1/2 Cl 2 (g) Na(g) + 1/2 Cl 2 (g) Na(g) + Cl(g) 0 +100 +200 +300 +400 +500 +600 +700 +800 -400 -300 -200 -100 NaCl(s) Lattice Enthalpy for Sodium Chloride Na + (g) + Cl - (g) H = -786 kJmol - 1 θLθL Na + (g) + Cl(g) Born-Haber Cycle for Sodium Chloride -- - --     kJmol -1