CO2 will have the lower vapor pressure than XeF2 because CO2 has stronger intermolecular forces of attraction due to the double bonds between the carbon and oxygen atoms. CH3OH will have the lower vapor pressure than CH3-O-CH3 because CH3OH can form hydrogen bonds between molecules, whereas CH3-O-CH3 only has weaker dipole-dipole interactions. Vapor pressure tends to decrease as intermolecular forces increase.

1. For each pair of substance identify the substance that is likely to have the lower vapor pressure.
Using IMF to explain your reasoning.
a. CO 2 or XeF 2
b. CH 3 OH or CH 3 -O-CH 3
Solution
Always remeber VAPOUR PRESSURE TENDS TO DECREASE AS THE
INTERMOLECULAR FORCES INCREASES.
a. CO 2 and XeF 2 both are non polar but in case XeF 2 there are more lone pairs on the
central atom which cause lone pair-lone pair repulson and bonds are easily broken so XeF 2
will have less intermolecular force of attraction while CO 2 having low vapour pressure as
double bonds are holding 2 oxygen atoms to carbon atom having higher intermollecular
force so CO 2 will have low vapour pressure.
b.CH 3 OCH 3 will have the higher vapor pressure. . CH 3 OH can hydrogen bond. CH 3
OCH 3 is polar (bent shape around the oxygen), so dipole-dipole forces will be the strongest
forces in this compound.