# What other byproducts come from the born-haber cycle?

Dec 11, 2014

The Born - Haber Cycle is usually used to calculate lattice enthalpies.

For sodium chloride this is $\Delta H$ for:

$N {a}_{\left(g\right)}^{+} + C {l}_{\left(g\right)}^{-} \rightarrow N a C {l}_{\left(s\right)}$

This can also be calculated using a theoretical electrostatic model assuming that the substance is made from discrete ions.

The work done in separating 2 charges ${q}_{1}$ and ${q}_{2}$ from a distance $r$ to infinity is given by:

$W \propto - \frac{{q}_{1} {q}_{2}}{r}$

Where $r$ is the separation.

By extending this idea to 3 dimensions we can calculate a "theoretical" value for the lattice enthalpy. By comparing the value of the experimental Born - Haber values with those obtained from the theoretical model we can get a measure of the ionic character of the bond.

Sodium chloride gives a very good agreement indicating that the ionic model we use is a good one. There is much more discrepancy between the values for silver chloride indicating more covalent character than would be expected if it were $A {g}^{+} C {l}^{-}$.