The boiling points need to differ by 50 degrees to enable their complete separation ie of two different liquids. The separation occurs by first evaporation of one of the liquids and then its condensation and collection. It is a physical process not a chemical one.
There are 18. In each molecule of Fe(NO3)2 there are 6 oxygen atoms because you have 2 nitrate (NO3) components which each contain 3 oxygen atoms. 2 x 3 = 6. Because you have 3 molecules of Fe(NO3)2, you need to multiply 6 by 3, which gives you 18 oxygen atoms.
Two non-polar molecules are most likely to interact by
induced dipole-induced dipole interaction.
Non-polar substances do not have a permanently established charge distribution due to similar electron affinities of the atoms that are present. Moreover, due to the absence of a polar hydrogen, they cannot exhibit hydrogen bonding. They interact with one another by induced dipole-induced dipole interactions which arise from the molecules of the substances coming into close vicinity of one another.
