# Why do aqueous solutions always “have to be” electrically neutral?

I was reviewing some analytical chemistry and stumbled upon a section that explained the imperfection of using a salt bridge.

It said that the using dissimilar ions is a problem because in, for example, the case of KCl the $K^+$ and $Cl^-$ have different mobility and so you get regions that are rich in $K^+$ and others rich in $Cl^-$. This means that some specific parts of solution (even though it's small) to be not electrically neutral i.e. electrically charged. So I imagine in theory at least it must be possible to somehow extract these charge-rich areas and put them into a beaker. So what is all this I've been learning about solutions having to be electrically neutral? Physics people?

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Is there some reason this isn't being asked on chemistry.stackexchange.com ? –  Chris White Apr 25 '13 at 5:08
It's talking more about the interaction of electrical charge more than some kind of chemical interaction. I feel that it is better suited for this audience for me to get the answer I'm looking for. –  Valentine Bondar Apr 25 '13 at 5:17

The same thing happens with your KCl solution. If you polarise it then split the solution you end up with a negatively charged solution with an excess of Cl$^-$ and a positively charged solution with an excess of K$^+$. There's nothing especially mysterious about this, and more than it's mysterious that a lump of metal can have a net charge.