Question

In reference to intermolecular forces, does benzophenone or benzil have a higher melting point? Also which of the 2 molecules has the strongest london dispersion force, dipole dipole force, and hydrogen bonding?

Answer 1

Benzophenone is a ketone, the C=O group makes it polar since it has a dipole movement will be towards the double bonded oxygen.
In case of benzil there are two keto groups, it has two C=O group and hence makes it more polar with a higher dipole moment.
So, the dipole-dipole forces will be more in case of Benzil and hence the melting point of Benzil (96.0 ^oC) is more than Benzophenone (48.5 ^oC).

Again, molecules having a higher relative molecular mass have stronger inter-molecular forces. Benzil molecular mass is higher than Benzophenone. With increasing molecular mass, the number of atoms in a molecule also increase, which means an increase in the elements (or atoms) of molecules. A molecule with a large molecular mass experiences stronger London Dispersion Forces. The reason is that longer molecules have more places where they can be attracted to other molecules.

Stronger london dispersion force - in Benzil
Stronger dipole dipole force - in Benzil, and
Hydrogen bonding - Both don't have the tendency to form hydrogen bonding among themselves.