Question

which imf influences bp most?
substance so₂ cl₂
imfs ldf and dipole-dipole ldf
molecular weight 64.1 g/mol 70.9 g/mol
bp 263 k 239 k
given the above information, which imf do you think has the most influence on the difference in boiling point between the two substances above?
london dispersion
dipole-dipole
hydrogen bonds

Explanation:

When comparing the boiling points (BP) of \(SO_2\) and \(Cl_2\), we note that \(Cl_2\) has a higher molecular weight. If London dispersion forces (LDF) were the dominant factor, \(Cl_2\) (with higher LDF due to higher molecular weight) should have a higher BP. But \(SO_2\) has a higher BP. \(SO_2\) has dipole - dipole forces (in addition to LDF) while \(Cl_2\) only has LDF. Since the presence of dipole - dipole forces in \(SO_2\) causes its BP to be higher than what would be expected from LDF alone (when compared to \(Cl_2\) with higher molecular weight but no dipole - dipole), dipole - dipole forces must be the more influential IMF in this case. Hydrogen bonds are not present as there is no \(H\) bonded to \(N\), \(O\), or \(F\) in either molecule.

Answer:

Dipole - dipole