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Author: Subject: Electrolysis of sodium carbonate with copper electrodes
Gustavo_Marzullo
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[*] posted on 20-3-2017 at 03:13
Electrolysis of sodium carbonate with copper electrodes


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I was doing this electrolysis and I found this:

1- The solution has gone from no colour to a light blue and, later, to a dark blue. I think it's due to the formation of de complex [Cu(H2O)4]2+.
2- A light greenish blue precipitate appeared.
3- Metallic copper started to accumulate in the negative pole. It's certainly because of the concentration of Cu2+ that is too high.

Does someone know what this precipitate can be? It can be Cu(OH)2, CuCO3 and Cu2(OH)2CO3.
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Melgar
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[*] posted on 20-3-2017 at 05:36


If the solution is basic, transition metals like copper will fall out of solution and not really plate well. Most metals dissolve much better in acids than bases. It's almost certainly copper carbonate you're seeing.

If you don't want your electrodes dissolving in solution, use graphite electrodes. You can pull them out of carbon zinc (heavy duty) batteries. If you do, try using an acid as your electrolyte.

[Edited on 3/20/17 by Melgar]
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Zyklon-A
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[*] posted on 21-3-2017 at 08:13


Basic copper carbonate. Neutral copper carbonate cannot form if water is around. I'm surprised that the solution has any color, all of the Cu2+ should have precipitated if CO32- was present.
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