[nj_bartel]

That would make sense.

[enahs]

Why do polar molecules not cause LDF's in nonpolar molecules, as nonpolar molecules do to themselves?

This is very poor wording. I am not sure what you are saying?
As I read it how you wrote it, you are wrong. Polar molecules do undergo electron motion and thus have induced-dipoles, and will cause an induced-dipole in other molecules, polar and non-polar. However, when a polar molecule with a dipole comes across a non-polar molecule, you have a dipole/induced-dipole scenario. The strength of this varies greatly with the poorly defined "polarizability" of the other non-polar molecule as well as the dipole moment of the polar molecule. But the "strength" of the dipole-induced/dipole-induced is typically smaller than a dipole/induced-dipole interaction; and so it is often ignored. Just like we ignore the dipole-induced/dipole-induced when we talk about a dipole-dipole interaction, it still occurs, but is not significant in comparison.

Maybe I am reading what you said wrong

[nj_bartel]

Uh, I'm not sure how to phrase what I was saying, but I think you got it.  It's my understanding then that the reason for polar molecules being insoluble in nonpolar molecules is that the dipole/dipole interaction is significantly stronger (and thus more stable) than the induced dipole/induced dipole interaction, and those preferentially forms, making the polar molecules cling to other polar molecules.

[enahs]

Here is a post I made a while back. It might not seem at first simplified, but it is very simplified explanation to explain the phenomenon of when and why things are soluble. And it is both qualitative and quantitative (thought I skipped all the math)! Not just "I think these forces are better then those forces" type stuff.
http://www.chemicalforums.com/index.php?topic=27861

It was typed up around simple ionic salts, but the same concepts apply.

[nj_bartel]

Nice post, thanks.

It does not because any entropy resulting from the disordering of the hydrogen bonded structure of the solvent water molecules is more then offset by the loss of energy from the breaking of the hydrogen bonds. You can say that the solute would willingly dissolve but the water is much more happy associating with its self.

Does this generally apply to polar solvents that don't have hydrogen bonds as well?

[macman104]

Wow Enahs, did you just pull that off the top of your head, or did you have to go look it up?  That's impressive to me if you can talk chemistry like that.

[Polleke]

I am gonna check your post more carefully later , however at first sight I think it will be to difficult to use your post enahs as a answer to this question for people that have alsmost no chemical background, knowledge.

I am gonna use what I wrote here:

when you have 2 substances that are both non polar, they mix because you break 2 non polar bonds (with vanderwaals forces) to form 2 new non polar bonds (with again vanderwaals forces) => energybalans is about the same, so they mix.

When you have a substance with polar bonds and one with non polar bonds and they WOULD mix , then you would break 1 non polar bond (vanderwaals forces) and 1 polar bond where you would break vanderwaals forces and strong polar -polar bonds.... when you put those 2 substances togheter you would only get vanderwaals forces back (non-polar + polar)  and thus the energy balance would not be the same.
You would need to put a lot more energy in the system (to break the polar-polar bonds) and would not get the same energy out the system when forming (if they would) non polar + polar bonds.

and use your answer for more background or a more correct story without going to much in detail.


I do find it strange that the saying dissolves likes dissolves is so well known , while hardly anyone has any taught about what it really means (besides that polar dissolves polar and non polar non polar).

[enahs]

Does this generally apply to polar solvents that don't have hydrogen bonds as well?

Non-aqueous solvents are complicated as well. And each one can be very different, it is very hard to give a broad explanation like water. A vast number of non-aqueous solvents behave as an acid or base (as does water) but it becomes more significant. You also have solvents such as carbon tetrachloride or cyclohexane which are non-polar, in essence nonsolvating and do not undergo auto-ionization.  You also can have polar solvents, yet they do not ionize to any appreciable extent (Acetonitrile, DMSO). The polarity of these solvents varies greatly and has a huge impact on their chemistry. There is also a non-commonly encountered in undergraduate chemistry a class of solvents that are highly polar and autoionizable, such as bromine trifuloride. These are highly reactive though, many will react with silica containers as well.

Throw into that the vast difference in permittivity, it because confusing when you try and do math.

There are many books on non-aqueous solvents. One of these days I will have some free time to read up them and will, as it is very interesting. I only know detail and explanations of a handful of non-aqueous solvents; and in those I do not see a simple explanation of comparison.  There might be, I just do not know it. Other then "chemistry man, chemistry".

Wow Enahs, did you just pull that off the top of your head, or did you have to go look it up?  That's impressive to me if you can talk chemistry like that.

General Chemistry and Analytical Chemistry pissed me to hell off. My teachers were always expecting us to remember suitabilities (and not just easy ionic suitabilities like in this chart I made to help people learn them) but also pKa's of stupid organic compounds. I was horrible at it. So in P-Chem we got to chose a topic to research and write about, so I chose that, as I wanted to learn why/what/when/understand. It turned out to be ~15 pages, lots of math, and great. More of a scientific approach to stuff and what I like.

It is only academic though. Gaining experience in lab using different solvents with different molecules, it quickly becomes intuitive based on "chemistry" (i.e. size, functional groups, etc) if it will be soluble in one solvent or another). There are always surprises, but generally experience is always correct.

I am gonna check your post more carefully later , however at first sight I think it will be to difficult to use your post enahs as a answer to this question for people that have alsmost no chemical background, knowledge.

I completley agree. Hence if you notice in the post before I typed it up, I said that trying to save my self work!
But there are various people reading this with various levels of chemistry, if it is useful to some great, if it just confuses others, bummer.

[macman104]

Wow Enahs, did you just pull that off the top of your head, or did you have to go look it up?  That's impressive to me if you can talk chemistry like that.

General Chemistry and Analytical Chemistry pissed me to hell off. My teachers were always expecting us to remember suitabilities (and not just easy ionic suitabilities like in this chart I made to help people learn them) but also pKa's of stupid organic compounds.

Yea, pKa's are no problem for me, I love that stuff!  But it becomes easy after a few upper organic classes.

I was horrible at it. So in P-Chem we got to chose a topic to research and write about, so I chose that, as I wanted to learn why/what/when/understand. It turned out to be ~15 pages, lots of math, and great. More of a scientific approach to stuff and what I like.

Ah, I see, fair enough.  Very cool!