Question

What is the equation for the reaction that represents the mean `"C-F"` bond energy in carbon tetrafluoride?

Answer 1

The equation is `1/4"CF"_4"(g)" → 1/4"C(g)" + "F(g)"`.

Explanation:

The bond dissociation enthalpy is the energy needed to break one mole of the bonds to give separated atoms, with everything being in the gaseous state.

Tetrafluoromethane, `"CF"_4`, contains four identical `"C-F"` bonds.

However, if you take `"CF"_4` to pieces one fluorine at a time, you will have to supply a different amount of energy to break each bond.

Each time you break a `"C-F"` bond, the environment of those left behind changes, and the strength of a bond is affected by what else is around it.

Thus, you would need to break the bonds in 0.25 mol of `"CF"_4` (1 mol of `"C-F"` bonds), and the total energy involved would then be the mean bond energy.

The thermochemical equation representing this process is

`1/4"CF"_4"(g)" → 1/4"C(g)" + "F(g)"`.