Thread replies: 6
Thread images: 1
Thread images: 1
File: Cu S2O8 cell.png (3KB, 400x400px)
3KB, 400x400px
It's me again, and I've changed my question. Is it possible for the following to happen by application of a potential difference?
[math]Cu^{2+}+2SO_4^{2-} \rightarrow Cu_{(s)}+S_2O_8^{2-}[/math]
Or will oxygen gas be released instead? According to the standard cell potentials and maybe a little common sense, oxygen gas will be released instead, but surely there's some concentration at which the reaction will happen the way I want it. I'm not experienced enough using the Nernst equation to know how to deal with solids and liquids messing up my reaction quotients, especially when calculating the individual half-cell reduction potentials.
Alternatively, are there any other oxidants I could use to replace the sodium persulfate? I know there are plenty out there at varying potentials, but most require acidic/basic conditions. If I was to "charge up" this cell and have to do so in acidic conditions, the cell would still be in acidic conditions when I want to "discharge" the cell, making it unfavourable. Would a stoichiometric quantity of acid work? I wouldn't be trying to extract any energy from the cell by discharging it, I'd actually just let it react with itself, would this make it less unfavourable?
The cell can be anything as long as it oxidises and reduces copper completely reversibly, and preferably uses easily acquired chemicals.
>>
>>8973344
Seems possible, but too lazy to make theactual thermodynamic calculations. Did you check the standard reduction potential? People who work on this make the calculations for every single route, so maybe you should do that as well.
Hopefully is not bigger than 1, or you get water decomposition as you say. Need to review the basics, if you find the answer post it anon.
>>
>>8973391
What potential do I need to use for the oxidation of water? Is it the 1.229V acid equation (in bold on the wikipedia data page) or the 0.401V hydroxide equation? I do plan on going through the full Nernst equations algebraically to find the answer I'm looking for, but I'll have to do it with the full cell potential, not with the individual reduction potentials.
A higher reduction potential means the reverse reaction (the oxidation) is less favoured, right? A solution of copper bromide looks somewhat promising, along with a couple of noble-metal chlorine complexes and a mysterious [math]I_3^-[/math] ion.
[math]CuBr_2 \rightarrow Cu_{(s)}+Br_{2(aq)}[/math]
Makes me wonder if the solution would have trouble conducting once the reaction is almost completed, I'd probably need a mixture of NaBr and CuBr2 and store it with the copper reduced out of it.
There are plenty of cations I could use instead of anions, but they'd probably have to be sulfates or some other soluble non-oxidisable-anion salt. Iron is the main one that comes to mind.
>>
>>8973420
what half reactions do you have? what potentials do your reactions have? what do you want to achieve?
>>
>>8973835
I want to be able to pull copper off one complicated source without direct electrical contact (a PCB), so I can't use electrolysis for this. Later I want to pull the copper out of solution onto a copper electrode with electrolysis. Any oxidant works, prioritising not producing any gas or solid, not requiring acidic/basic conditions, and being largely non-toxic.
Is the following reaction plausible?
[math]CuI_2+NaI \rightarrow Cu_{(s)}+NaI_3[/math]
I'm not too sure which oxidation state the copper in solution will be, which is a problem.
>>
Nernst gives me -1.72V in assumed conditions from the -1.67V standard potential, it doesn't look like I'll be able to get it below (above?) the standard potential for the oxidation of water and reduction of copper, which is -0.89V. Not sure how to figure out the reaction quotient of oxygen being released into a ventilated room, but it shouldn't change it too drastically. But will the lack of acid in the solution make the production of oxygen extremely unfavourable?
Looks like bromide or triiodide is the way to go, and triiodide will put me on the terrorism watchlist. I can get 50g of CuBr for $16 US, which looks like a pretty good deal.
Thread posts: 6
Thread images: 1
Thread images: 1