Hello, I'm having trouble identifying what intermolecular forces are at play based of a chemical formula. For instance
Based simply on the molecular formula pro-
vided, which of the following compounds is
least likely to be miscible in cyclohexane
1. methanol (CH3OH) correct
2. benzene (C6H6)
3. phenol (C6H5OH)
4. Each contains a hydrocarbon unit and
should be equally miscible.
5. naphthalene (C10H8)
I don't understand why benzene or napthalene aren't more miscible in C6H12 since "like dissolves like" and the intermolecular forces are what determine miscibility and these seem to have similar IMF's and the methanol is a polar molecule which violates the "like dissolves like" ??
Also: 1. Rank the following in order of decreasing vapor pressure:
Ar, NH2, TiO2, C6H6, CH3OH, LiBr, CH2Cl2, C2H6.
1. TiO2 > LiBr > NH2 > CH3OH > CH2Cl2 > C6H6 > C2H6 > Ar.
2. Ar > C6H6 > CH2Cl2 > C2H6 > CH3OH > LiBr > NH2 > TiO2.
3. Ar > C2H6 > C6H6 > CH2Cl2 > CH3OH > NH2 > LiBr > TiO2. correct
4. Ar > C2H6 > C6H6 > CH2Cl2 > NH2 > CH3OH > LiBr > TiO2
This is where I'd get the most help from, how do I find out what IMF's exist within a molecular formula? For instance I understand there's an inverse relationship between the strength of the IMF and the vapor pressure i.e. a strong IMF = weak vapor pressure.
I think AR has the weakest IMF since the only IMF is Van Der Waal forces since it's a noble gas which means no dipole no hydrogen bonding and no ion-ion interaction..
However, why isn't CH2Cl2 ahead of C6H6? There's more hydrogen bonds in the C6H6 which constitutes a stronger IMF right?
Actually I'm quite confused as to why the order goes for all of them except for the AR, can someone please explain to me a more quanitative or qualitative way of figuring out relative IMF strengths of molecules? Thanks.