Answer:
HF is electronegative compared to O2. HF has delta plus and delta minus creating a dipole moment, it is a polar molecule therefore it has a higher boiling point. O2 which is symmetrical and non polar (looks like O=O) and therefore has no dipole moment. Hydrogen bonds are hydrogen with N, O and F - the most electronegative elements. This makes the polarisation of the bond much stronger, and so the dipole-dipole bonding between them is stronger. (Since it is the attraction between partial positive charge and a partial negative charge, the larger the polarisation.
