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Today I experimented with different solvents and solutes and was a bit surprised by one result. When I added ethanol to dilute sodium bicarbonate and tapped the test tube against my palm to mix it, I saw the mixture swirling, then it turned cloudy.

I don't understand why this happened -- as far as my understanding goes, ethanol is both a weak acid and a weak base, and it dissolved with NaOH and HCl with no trouble. Does this have anything to with the fact that ethanol and sodium bicarbonate are both amphiprotic? Or is there a different explanation?

Thanks in advance.

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    $\begingroup$ You are asking the wrong question. You should be asking why sodium bicarbonate is less soluble in water/ethanol mixtures than it is in water. it isn't ethanol failing to mix with water that is making the result cloudy. $\endgroup$ – matt_black Sep 17 at 10:25
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Firstly ethanol being an organic compound, tends to dissolve less in polar compounds. But it can form numerous hydrogen bonds in water and hence is soluble in most aqueous solutions. NaOH is a often considered a moderate base in organic chemistry. If you dissolve ethanol in aq.NaOH , it tends to oxidize the alcohol into its aldehyde which further undergoes aldol reactions, giving it a yellowish brown color when left for many days.

That is not the case with NaHCO3 as its an even weaker base, so it rarely participates in any reaction with ethanol. Also there are lesser possible hydrogen bonds per molecule in it. So its already less soluble in polar solvents like H2O, not to talk about in organic solvents like ethanol.

Hope this helps.

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    $\begingroup$ What tends to oxidise alcohol? Certainly not NaOH... $\endgroup$ – Mithoron Sep 17 at 15:55
  • $\begingroup$ Neither did it seem much convincing to me at first, though I couldn't have been much sure about reactions that take a days to occur, so I just knew it as a fact, though I am sure that NaOH cant oxidize ethanol. But it was what I learnt from a site while surfing the net, here goes the link--reddit.com/r/chemistry/comments/48c0ai/… perks of not trying to take a second opinion. $\endgroup$ – Sir Arthur7 Sep 17 at 18:59
  • $\begingroup$ Well, I guess OP wacky reasoning got you fooled. Acid base equilibria are largely irrelevant here. You can rewrite your post, for example using things like en.wikipedia.org/wiki/Solvent for help also solubility tables etc. $\endgroup$ – Mithoron Sep 17 at 20:24
  • $\begingroup$ Yes you are right it seems, I have corrected my false beliefs now. But don't you feel in this age of technology and with so easy access to internet around the globe, sites like Wikipedia are the ones that anyone searches for at first and hence there's nearly no need to share links to that? For me links to other useful, legitimate, and less searched docs is more appreciated $\endgroup$ – Sir Arthur7 Sep 18 at 4:15
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Sodium bicarbonate is a ionic compound with quite limited solubility in water. Ethanol is worse solvent to dissolve ionic compounds than water is, as it is less polar. Therefore salts have generally worse solubility in ethanol than in water.

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