Bonding

Explain why the boiling temperature of PH3 is greater than that of CH4.

So I think that CH4 only have van der waals forces due to the symmetry of the molecule? There was a question previous to that worth 3 marks asking why a CH4 molecule has no overall polarity. I said something to do with it's tetrahedral shape and that the polarity cancels out. If someone could help me expand on that it would be appreciated.

So my question is how do you know when the symmetry cancels the polarity and when it doesn't? I am not exactly sure about the intermolecular forces in PH3. I am pretty sure it has van der waals but not sure if it also has permanent dipole-dipole?

Thanks :smile:

Original post by Super199

Explain why the boiling temperature of PH3 is greater than that of CH4.

So I think that CH4 only have van der waals forces due to the symmetry of the molecule? There was a question previous to that worth 3 marks asking why a CH4 molecule has no overall polarity. I said something to do with it's tetrahedral shape and that the polarity cancels out. If someone could help me expand on that it would be appreciated.

So my question is how do you know when the symmetry cancels the polarity and when it doesn't? I am not exactly sure about the intermolecular forces in PH3. I am pretty sure it has van der waals but not sure if it also has permanent dipole-dipole?

Thanks :smile:

Draw out the 3-dimensional shape of PH₃ and you will see why ...