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

1 Answer
Owen Bell
Dec 31, 2015

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"#

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