Help with chemistry question about polarity of molecules and IMAFs

Question

Carbon dioxide (CO2) has a boiling point of -57C and water (H2O) has a boiling point of 100C. A molecule of CO2 has a mass of 44.0 amu and a molecule of H2O has a mass of 18.0 amu. Why then, if CO2

is a larger molecule than H2O, does H2O have a boiling point that is so much higher? Explain in

terms of the polarity of each molecule and its resulting effect on the strength of the attractive

forces between the molecules.

Answer 1

H₂O has a higher boiling point than CO₂ mainly because of the much stronger IMAFs present in H₂O. The forces in H₂O are hydrogen bonding and because it is a polar molecule, it also has dipole-dipole attraction. CO₂ on the other hand is not polar and so has only London dispersion forces. The stronger IMAFs in H₂O account for the higher boiling point.