i am an AP lungemine.com student and there is a little detail concerning polarity of molecules that i am perplexed about.

My review book (Princeton review) claims that ethanol has stronger intermolecular pressures than methanol due to the fact that it has actually a huge molecular mass and is therefore an ext polarizable and much more soluble in water than methanol.

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Yet, my lungemine.com textbook claims that both ethanol and also methanol space miscible in water, however the more the carbon chain increases, the much less miscible the becomes. Further supporting this statement is the reality that methanol is less soluble in hexane, a nonpolar substance, than ethanol. As such ethanol is much less polar. Plus, heptanol is hardly soluble in water, yet according to the Princeton Review"s logic, it must be even much more soluble in water than methanol since it has actually a bigger molecular mass.

So, i m sorry is it? does the enhancement of CH3s do a molecule much more or less polar, and much more or less miscible in water?


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inquiry Feb 22 "17 at 19:35
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JessJess
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If your book says specifically that, climate it claims nonsense. Sure enough, the addition of CH2"s renders a molecule less polar. Together for the solubility in water, methanol is miscible - i.e., infinitely well soluble in it. So is ethanol. Just how would you to compare the two infinities?

That being said, the bigger molecule the ethanol is indeed much more polarizable (not more polar, mind you!), and has more intermolecular interactions per molecule than methanol, which accounts because that the greater boiling point.


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answer Feb 22 "17 at 20:21
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Ivan NeretinIvan Neretin
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mine review book (Princeton review) claims that ethanol has actually stronger intermolecular forces than methanol because it has actually a big molecular mass and also is therefore more polarizable

True

Ethanol does ~ above a molecule by molecule basis have actually stronger intermolecular forces in between itself and water than methanol and also water.

and more soluble in water than methanol.

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False

Yet, my lungemine.com textbook states that both ethanol and methanol are miscible in water, but the an ext the carbon chain increases, the much less miscible the becomes.

True

Why?

As you boost the number of carbon-chain linkages the polarizibility that the molecule does in reality increase.

However, the point that makes tiny chain alcohols dissolve in water is not the truth that you can induce a non-polar shortcut to have actually a brief lived neighborhood dipole (van der Waals forces), but since of the permanent dipole of the alcohol group. The hydrogen on a alcohol (or water) is very positive and the oxygen is very negative, so they lure other polar groups around them in a reasonably well notified manner. For brief chain alcohols the alcohols in ~ the end of the chain deserve to take the ar of the oxygen and also hydrogen on other water molecules and with the entropy natural with mixing deserve to be miscible with water.

For long chain alcohols the non-polar chains deserve to be polarized, but they carry out not interact with water nearly as strongly as other waters and the entropy natural with mixing is not enough to counter the power difference. And also so if over there are any kind of other waters "nearby" the water molecules will certainly self-segregate, together water is an ext attracted to other waters than to the non-polar chains the they room inducing into forming dipoles.

As friend add more alkane linkages the molecule becomes less polar but an ext polarizible - yet this does not include much (comparatively) come the solubility the a non-polar molecule in a very polar solvent like water contrasted to very polar groups.