Miscibility question

[FeralisExtremum]

Came across this in Qvault:

How are n-hexane and water more miscible than dichloromethane and water? Dichloromethane is polar and water is polar, it doesn't make sense to me that a nonpolar compound could somehow be more miscible. The answer explanation seems to be contradictory as well.

Also, for those of you who have taken the DAT: how does Qvault Ochem compare in difficulty? Some of these questions seem to be coming out of nowhere...

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[Koalafied]

Came across this in Qvault:

How are n-hexane and water more miscible than dichloromethane and water? Dichloromethane is polar and water is polar, it doesn't make sense to me that a nonpolar compound could somehow be more miscible. The answer explanation seems to be contradictory as well.

http://en.wikipedia.org/wiki/Dichloromethane

 

[FeralisExtremum]

Ok, can you tell me why it's not miscible with water?

 

[Koalafied]

Ok, can you tell me why it's not miscible with water?

Look, don't make this question more complicated than it needs to be. You know that dichloromethane can only be mixed in one way: treating/dissolving like with like. If you use the dichloromethane besides water, such as H2O or D2O, you'd end up with immiscibility since it's a polar solvent and those are immiscible. Water is immiscible to dichloromethane since it is a strong polar solvent but terrible organic solvent on account of its polarity. Organic solvents would give us a different mix and wouldn't even be an option here since it's a miscible combination, so you can knock out the organic solvents answer choices.

The shortcut to this is dichloromethane is not miscible in water, but miscible in many organic solvents.

 

[FeralisExtremum]

Look, don't make this question more complicated than it needs to be. You know that dichloromethane can only be mixed in one way: treating/dissolving like with like. If you use the dichloromethane besides water, such as H2O or D2O, you'd end up with immiscibility since it's a polar solvent and those are immiscible. Water is immiscible to dichloromethane since it is a strong polar solvent but terrible organic solvent on account of its polarity. Organic solvents would give us a different mix and wouldn't even be an option here since it's a miscible combination, so you can knock out the organic solvents answer choices.

The shortcut to this is dichloromethane is not miscible in water, but miscible in many organic solvents.

You didn't really answer my question. Like dissolves like. Dichloromethane and water are both polar. So what is it about dichloromethane that makes it immiscible with water despite its polarity? You just sort of strung together a bunch of unrelated facts as an explanation...

 

[Minion]

Dichloromethane would be nonpolar, if you use symmetry you can see that the chloride are possibly mirror images with each other. Perhaps an internal mirror image, also it has bunch of carbons which would definitely make it towards nonpolar. Nonpolar dissolves with nonpolar. Hope this helps !

 

[Minion]

Dichloromethane would be nonpolar, if you use symmetry you can see that the chloride are possibly mirror images with each other. Perhaps an internal mirror image, also it has bunch of carbons which would definitely make it towards nonpolar. Nonpolar dissolves with nonpolar. Hope this helps !

Oops, I was thinking of a different molecule.

 

[Illfavor]

Polar, yes...But it can't hydrogen bond. There are exceptions to every rule!

 

[supergenius310]

Polar, yes...But it can't hydrogen bond. There are exceptions to every rule!

What he said is right. Water molecules are indeed polar ...but are miscible with molecules that have hydrogen bonding. Dichloromethane is not as polar as you think... it is actually considered almost nonpolar. n-Hexane would have BETTER solubility than water in this case.

Hope that helps.

 

[Toadesque]

My ignorance would have gotten me this question correct lol, I just figured the methane aspect would have made it more non-polar so it would be miscible with hexane.

 

[emitpeels]

Likes dissolve likes. You chose polar and non polar. These two together will not dissolve. So two non polars will dissolve.

 

[Illfavor]

Likes dissolve likes. You chose polar and non polar. These two together will not dissolve. So two non polars will dissolve.

Well, not technically. DCM is polar.