KiRhoSigma
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Reaction of Hypochlorite with Cu
I'm curious about something. So, recently, I was wondering whether hypochlorite could bring copper up to a higher oxidation state than Cu(II). So I
mixed copper sponge that I'd prepared from CuSO4+Mg with an excess of bleach. Slowly, the copper began to darken, and give off a few bubbles of gas.
Upon standing for 30 minutes, the supernatant liquid above the copper had turned a pale purple/pink color. I then added ca. 5 mLs of saturated
Cu(OAc)2 solution to an equal amount of bleach, which caused the formation of a fine dark black precipitate, mild effervescence (no strong chlorine
smell, though), and a color change of the bleach rapidly to a similar color to that from the reaction tube with Cu metal, but more saturated. I'm
fairly sure that the precipitate and coating on the surface of the Cu sponge is CuO, but what I'm curious about is the reason for the pink/purple
color of the solution. What reaction is occurring? What species does the solvated copper form?
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Fantasma4500
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i know in the fireworks industry copper oxychloride is used to improve some rocket fuels, ive always wondered how to make this, could be you made
that?
also for making copper metal another time just use steel wool and CuSO4
ill leave your question to be answered by others however
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blogfast25
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Unstable (or metastable?) oxidation states III and even IV are known for Cu. And since as hypochlorite is one of the most powerful oxidisers and in
both cases you obtained some colouration it seems logical to attribute it to an oxidation state of > II. So I assume the hypochlorite has caused
some of the Cu (II) to oxidise to Cu (>II). (The black CuO is probably due to alkalinity of the bleach).
But how to prove this? The main problem I see is that your solution is likely to contain residual hypochorite. The copper III or IV will be a very
strong oxidiser but its hard to test for it in the presence of another strong oxidiser. You may need to work quantitatively for this.
As a first approach, I would add some solution of Mohr's Salt (the double salt of ammonium sulphate and ferrous sulphate) to the pink/purple solution.
The ferrous ions are easily oxidised to ferric ions and that should make the pink/purple disappear: Cu (>II) + Fe (II) === > Cu (II) + Fe (III),
and yield a blue solution.
I could be wrong but I seem to recall woelen's done some experiments with unusual Cu oxidation states.
[Edited on 5-10-2013 by blogfast25]
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