Question

When would a molecule with only London dispersion forces/induced dipole-induced dipole have a higher boiling point or melting point than a molecule with stronger intermolecular forces? Some examples of these cases would be nice. My best guess is when the molecule w/ London dispersion forces is a solid compared to something else w/ H-bonding or dipole-dipole that's a gas. But I am not positive about that.

Answer 1

There are four types of weak vanderwal forces ...

1) lodon forve- this act in non polar molecules like Cl2,Br2etc..and it is very weak in nature so have lowest boiling and melting point.

2)dipole induced dipole attraction force- this act between polar amd non polar molecule like HCl andCl2.and stronger then lodon force so have higher BP and MP.

3)dipole- dipole attraction force- this is between polar molecules like HCl and HCl and stronger than second one so have high BP and MP..

4) H-Bond- this is special type of weak attraction which act between Hydrogen and high electronegative elements like Florine,oxygen and nitrogen ..and stronger then above tree forces that's why have high BP and MP..

So order of bond energy 1<2<3<4

And order of BPand MP 1<2<3<4