Question

What other byproducts come from the born-haber cycle?

Answer 1

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

For sodium chloride this is `DeltaH` for:

`Na_((g))^++Cl_((g))^(-)rarrNaCl_((s))`

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:

`Wprop-(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 `Ag^+Cl^-`.