The chemical reactions when you pass a current through Nacl with Copper electrod

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Offline Pauline Solari

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Hi - I was looking at the electrical conductivity of solutions with my 11 year old the other day and I have some questions.

We were using Na Cl dissolved in distilled water and we had 2 copper electrodes. we passed a 12-volt current through.

I understand that at the anode we have 2Cl --> Cl2 (g) + 2e- and at the same time Cu(s) --> 2e- + Cu 2+ (aq) causing an oozing browish green stream from the electrode

I also understand that at the cathode we have 2H+ (aq) + 2e- -->H2 (g) and Cu2+(aq) + 2e- --> Cu (s)

What I don't understand though is what the brown (rust coloured) sediment is that we have in the dish after a period of time - ??copper chloride or ??copper oxide???? or??????.

Also, what happens to the Na+ ions and the OH- ions???

Can anyone explain this please and also how do both hydrogen and Cu2+ pick up e- from the cathode, but not the Na + and why chlorine gives off it's electrons at the anode and not OH-??

many thanks


Offline Chemistry4me

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Can you imagine what would happen if Na+(aq) turned into Na(s)?  [:-\]

Something like this:


Online Bored chemist

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The brown sludge is mainly Cu2O.
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