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When you're doing a boiling point problem first make sure that you are looking at intermolecular forces, not intramolecular forces, because this has to do with phase changes. When I look at boiling point problems I first look to see what types of intermolecular forces are involved and I look for the strongest first, then the weakest. This means I look for whether or not the molecules have hydrogen bonding, then some type of permanent dipole force, then dispersion forces. Generally, look to see which molecule has a type of intermolecular force that the other doesn't have. And if they both have all of the same intermolecular forces involved then you have to look at the strength of the specific intermolecular force.
It depends on what you are comparing. But the most important factors should be the IMF (intermolecular forces) that are broken when the molecule is boiled. For example if comparing anything with a hydrogen bond (ex. HF) to another molecules say with only London dispersion forces (ex. HCl) then the molecule with hydrogen bonds which are stronger than London dispersion forces will have a higher boiling point. If comparing two molecules with both only London dispersion forces, then the molecule with more London dispersion forces (larger in size) will have a higher boiling point. Finally when comparing two molecules with dipole dipole forces, the molecule with the more highly electronegative atom will have a higher boiling point because it will be more ionic than covalent in character.
If there is one compound with weak dipole-dipole interactions, and another compound with a large molar mass and many electrons (so therefore strong London Dispersion Forces), which one would have the greater boiling point? Is it possible that strong LDFs can result in a higher boiling point that a compound with weak dipole-dipole interactions?
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