List the compounds in decreasing boiling point order. ch3ch2ch3 ar ch3cn

The boiling point depends on the strength of the intermolecular forces holding the molecules together. Greater the force, higher is the boiling point.

The intermolecular force increases in the order shown below:

ion-ion > H-bonding > dipole-dipole > London dispersion

CH3CN is a polar molecule with strong dipole-dipole forces

CH3CH2CH3 is non-polar held by london dispersion

Ar exist as a gas. It will have a lowest boiling point

Thus the order of decreasing b.pt is:

CH3CN > CH3CH2CH3 > Ar