Question #7551d

1 Answer
Jun 16, 2017

see below


It is the polarity of a substance that affect the boiling point, not the contrary. That is because the intermolecular bonds, that must be won from the cinetic energy (that is proportional to the absolute temperature), more are strong, more they need high temperature.

Furthermore as bigger is the molecular mass as bigger must be the energy you must be given to the substance to move the molecules and break its intermolecular bonds.

The strongest intermolecular bond is H bond. You have this kind of bonds double in water (MM= 18, Teb = 100°C), and simple in ethanol (MM= 46 Teb= 78°C) and affects also F and N when this atoms are present.
Then come the polar bonds between polar molecules.

The weakest intermolecular bonds are between apolar molecules as Cycloexane (MM=84 ; Teb = 80°C)