Question

for each of the following pairs of molecules, which one is the higher boiling point?

1) CH4 or CH3F
2) CH3OCH3 or CH3CH2OH
3) C2H6 or C3H8

Answer 1

(1)

CH3F has a higher boiling point because it has higher molecular mass. Also since it contains F, so dipole dipole interactions are also present in CH3F, which makes the boiling point higher.

(2)

CH3CH2OH has a higher boiling point, because although the two compounds have same molecular masses, there is hydrogen bonding present in the alcohol CH3CH2OH, which is not present in the ether CH3OCH3.

So presence of hydrogen bonding in CH3CH2OH makes its boiling point much higher.

(3)

C3H8 has a higher boiling point because its molecular mass is higher which means it has stronger Van Der Waal's forces of attraction between its molecules.