Question

What are the intermolecular forces of CHF3, OF2, HF, and CF4?

Answer 1

The strongest intermolecular forces in each case are:

• `"CHF"_3`: dipole - dipole interaction
• `"OF"_2`: London dispersion forces
• `"HF"`: hydrogen bonding
• `"CF"_4`: London dispersion forces

Explanation:

Each of these molecules is made up of polar covalent bonds; however in order for the molecule itself to be polar, the polarities must not cancel one another out. The polar bonds in `"OF"_2`, for example, act in opposite directions and are of the same electronegativity difference [`Delta("EN")`], so the molecule is not polar. A similar principle applies for `"CF"_4`. As a result, the strongest type of intermolecular interaction between molecules of these substances is the London dispersion force .

Due to the fact that the polar bonds do not cancel in the remaining molecules, they exhibit dipole - dipole interactions: these are stronger than London dispersion forces. However, `"HF"` exhibits hydrogen bonding - a stronger force still that is similar to the dipole - dipole interaction - whilst `"CHF"_3` does not. Thus, strength of intermolecular forces between molecules of each of these substances can be expressed, in terms of strength, as:

`"CF"_4 = "OF"_2 < "CHF"_3 < "HF"`