Why does ch3coch3 has stronger intermolecular forces than c2h5oc2h5? even though both have dipole-dipole as their imf, but c2h5oc2h5 has a larger molecular weight and as the molecular weight increases, the imf get stronger. so why it is the opposite here?

I think because the CH3COCH3(second picture) has a ketone(the double bond to oxygen C=O) in the chemical structure and I believe ketones lead to stronger IMF than ethers(C-O-C). I am not sure about this, but I hope this answer will at least help give you a hint as to what to look up to figure this out. I'm sorry I couldn't be of more help! 

This is not a full question, text me and i'll you

If the water vapor content stays the same and the temperature drops, then the relative humidity increases. its vise versa.if the water vapor content stats the same and the temperature rises, the relative humidity decreases. so, yes, i'd say that temperature and humidity have a strong relationship.