Why doesn't silica gel dissolve in ethyl acetate when something like aspirin does. Both silica gel and ethyl acetate are highly polar. I though like dissolved like.
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2Neither aspirin, nor ethyl acetate are highly polar, but rather moderately. – Mithoron Sep 11 '15 at 00:00
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2@Mithoron, add the fact that silica is a network solid, so it does not dissolve in much of anything (except for what reacts with it), and you have good answer. – Ben Norris Sep 11 '15 at 01:31
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1If "like dissolves like" were the only rule, then your bathtub would get dissolved in water, together with much of your kitchenware. Oh, and your car would be gone completely, because it has both polar and non-polar liquids in it. – Ivan Neretin Sep 11 '15 at 06:26
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but seriously. if that rule is incorrect, why is it taught. i guess its akin to the i before e rule. – sean Sep 11 '15 at 23:55
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3Come on. Every empirical rule has its limitations. – Ivan Neretin Sep 12 '15 at 11:46
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1It is not incorrect, it is just limited. – orthocresol Oct 12 '15 at 12:27
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Not even methanol or water do a good job of dissolving silica gel (although water is better at it than most other solvents). I haven’t actually tried DMF, which is supposed to be one of the most polar solvents out there, though. – Jan Oct 12 '15 at 12:32
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@BenNorris Silicon dioxide does dissolve in hi-pressure hi-temperature water. http://www.minsocam.org/ammin/AM62/AM62_1052.pdf – permeakra Jan 17 '16 at 12:44
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Because (among other things) silica is not actually polar. Yes, theoretically a molecule of $\ce{SiO2}$ should have some degree of polarity to it. However, silica as a solid does not exist as single molecules.
Silica exists as a network of $\ce{Si}$ cations bonded together by $\ce{O}$ anions. One way of looking at it would be to say that each small bead of silica gel (or any other form of silica, glass or quartz) is one huge single molecule of silica.
