Question

From these chemicals which has the lowest boiling point? (HINT: Draw Lewis Structure)
H2O CH30H CH3-0-CH3 CH3CH3 Chose one

Answer 1

The boiling point of a compound(whether it will be high or low) can be predicted by the nature of cohesive force that binds the molecules of the compound, i.e the nature of intermolecular forces. The stronger bonds will need more heat to break itself resulting in higher boiling point. For example, the ion-ion interaction force are very strong whereas the dipole-dipole interacrtion are comparitively weak. lets see the type of intermolecuar forces in above molecules.

molecule     bond type          strenght

H2O:       hydrogen bonds. medium

CH3OH   hydrogen bond      medium

CH3-O-CH3 H-Bond           medium

CH3CH3     london forces    weak.

So, CH3CH3 has the lowest boiling point