December 07, 2022, 02:38:53 AM
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Topic: Trouble with a mixed solution of copper (II) chloride and copper sulphate.  (Read 538 times)

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Offline almannn

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I have gotten a solution of a mixture of copper chloride and copper sulphate I was hoping to recover some of the copper to use for future projects. I have tried produced copper carbonate with sodium carbonate solution in excess and filtering, however doing this still left a blue solution along with some copper carbonate.

What can be left in the blue liquid that has been filtered off? I tested the liquid with sodium carbonate and no precipitate forms... Have I missed something here?

Both copper sulphate and copper chloride reacts with sodium carbonate right?

Offline Borek

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #1 on: November 02, 2022, 12:17:47 PM »
First of all - what is pH of the solution?
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Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #2 on: November 03, 2022, 04:30:01 AM »
Very basic, roughly into 11 with the indicator paper I have on hand.

Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #3 on: November 03, 2022, 04:41:36 AM »
With that in mind I did add some sulphuric acid and it went clear once neutralised... Still not sure about what it could be since chemistry isn't my background.

Offline Borek

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #4 on: November 03, 2022, 06:14:31 PM »
With that in mind I did add some sulphuric acid and it went clear once neutralised...

Was the original solution clear, or murky?

If it was bluish it definitely still contained some copper. Could be you dissolved suspension and it got less visible, but the copper could not disappear.
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Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #5 on: November 04, 2022, 04:22:03 AM »
I'm pretty sure the solutions were made from lab reagent solids before being mixed, the solution was blue yet clear not really cloudy...

I just tested the blue filtrate (about 25 millilitres) by adding a couple of pipette of 5M sulphuric acid and it went clear and neutralised. I've just tried added sodium hydroxide and the solution turns blue again! This to me seems like copper hydroxide is made right? Maybe it's just really dilute though idk?

I'm also sure that treating the solution in excess sodium carbonate that I've removed and extracted most of the copper as carbonate (I got a good amount). I'm currently thinking maybe there was some over copper salt not known or a copper complex that wouldn't react with sodium carbonate and that is what is left in the filtrate solution? Googling I wasn't able to find a good candidate of a copper salt it could be.

I am going to try heating the solution slowly and see if copper oxide will be made as a last resort. Or if that doesn't do anything I'll just dispose it as dilute copper sulphate/chloride waste. Thanks for trying to help btw!

Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #6 on: November 04, 2022, 06:23:11 AM »
I've just heated a sample and it turned black so I'll try and dispose of the copper oxide that way once the solution is clear. Just unsure what the actual copper salt that was left over was ¯\_(ツ)_/¯.

Offline Borek

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #7 on: November 04, 2022, 04:35:40 PM »
Salts are dissociated, so it is not simply a "salt". You have a solution with a mixture of ions, between them some copper (could be in a complexed form). Often there are many ways of producing identical solutions, so in the end there is no way to tell what "salts" it contains - at best we can list all ions separately.
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Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #8 on: November 06, 2022, 12:38:23 PM »
Yeah I understand what you're saying about the ions so I guess I can walk through it so I can learn something: Given the solution to start with with Copper chloride (Cu2+ and 2Cl-) and Copper sulphate (Cu2+ and SO42-). Reaction with Sodium carbonate adds 2Na+ and a CO32-. With the displacement reaction of the chloride ions and sulphate ions in excess by carbonate ions, how would there be any copper left in solution? Is there something I'm missing in this regard? Is there just copper ions in solution once the copper carbonate precipitate comes out?

By washing the precipitate out I get that I remove the soluble ions from the filtrate which would be Na+, Cl- and SO42- ions, as well as some Cu2+ ions given the solution is still blue right?

Offline Borek

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #9 on: November 06, 2022, 02:57:29 PM »
With the displacement reaction of the chloride ions and sulphate ions in excess by carbonate ions, how would there be any copper left in solution?

There should be not (edit: Ksp of the carbonate is in the 10-10 range, so with an excess of CO32- I would expect something like nM solution, negligible) - but if the solution is blue, probably some are left. Most likely in some complexed form (otherwise it should precipitate), which suggests to me solution contained something more that just pure copper chloride and sulfate.

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Is there just copper ions in solution once the copper carbonate precipitate comes out?

In general - assuming solution contained only ions mentioned earlier - you remove Cu, but everything else is there. Cl-, SO42-, Na+, excess CO32- (not to mention HCO3- from the hydrolysis, plus OH-; there will be also traces of other ions - like H+ and HSO4- - but their amounts will be orders of magnitude lower). Charge balance says something like

[Na+] + [H+] = [Cl-] + 2×[SO42-] + [HSO4-] + 2×[CO32-] + [HCO3-] + [OH-]

(not that it matters much in this particular case, but is a general and important property of such solutions, technically traces of copper should be also included on the left, together with several forms of complexed copper ions - all in trace quantities).

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By washing the precipitate out I get that I remove the soluble ions from the filtrate which would be Na+, Cl- and SO42- ions, as well as some Cu2+ ions given the solution is still blue right?

More or less yes.

Note that what you precipitate is not a simple copper carbonate, it is kind of a mixture of basic copper carbonates with typically a slightly variable composition.
« Last Edit: November 07, 2022, 05:12:42 AM by Borek »
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Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #10 on: November 07, 2022, 08:47:11 AM »
Thanks for the info it has been fun to learn about. I knew I was making basic copper carbonate I was just being lazy not adding that. The complex whatever it is fell out into copper oxide when heated anyway and left a colourless solution so I'm happy with that result.

Currently just drying the basic copper carbonate from a sludge to hopefully a powder but it's taking awhile as it's getting cold. I'll just dispose the copper oxide as I only a tiny bit from it.

I come from physics background so chemistry generally isn't what I'm used too, I'm sure I'll learn as I go.

Offline Borek

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #11 on: November 07, 2022, 09:16:10 AM »
On a practical side chemistry is much worse than physics. Sure, it is an exaggeration to say that physics experiments always work as expected, but looking from the chemistry side - they do ;)
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Offline almannn

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Re: Trouble with a mixed solution of copper (II) chloride and copper sulphate.
« Reply #12 on: November 25, 2022, 06:22:16 AM »
https://ibb.co/64FmnSq

I managed to get most of the copper carbonate and it looks quite pure but didn't have the time to collect it and label, There was a tiny bit of copper oxide though so I added that as a trace. Don't think it'll matter too much though!

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