Can I convert copper(II) acetate or carbonate to copper(II) sulfate?

Question

I am a high school student who does chemistry as a hobby, and as such I really don't know very much. I managed to make some copper(II) acetate and copper(II) carbonate, and now I'd like to convert it into copper(II) sulfate (mostly for the purpose of electroplating).

I do have sulfuric acid and I understand that I could react the copper compounds with it to make copper sulfate. However, the sulfuric acid I have claims to have metal inhibitors, and I don't know if that will impede the reaction.

It would be really interesting to me if I could take elemental sulfur and use it in the conversion process, because I do have a good amount of that.

Answer 1

Practical approach

Arguably, the easiest way is to trade/exchange your chemicals — copper(II) salts and elemental sulfur — for copper(II) sulfate, which should be readily available for purchase online or from a gardening store as it's considered both fungicide and fertilizer. Since you are going to use the sulfate for electroplating, it doesn't matter much whether you get an anhydrous salt or a hydrate. This way you will save energy, time, resources and will be aware of the purity.

Although it's perfectly doable in a chemical lab, I would advise against conversion of elemental sulfur to sulfate as it requires a harsh conditions and a strong oxidant (hydrogen peroxide, chlorine/bromine water) and is not only time-consuming and arduous, but is also a bit dangerous, and given the availability of vitriol, the risk is just not worth it. At all.

For educational purposes you can use sulfuric acid, the chemistry is pretty straightforward. If you need to isolate a relatively pure product, you will need to crystallize the product $(\ce{CuSO4.5H2O})$ from the saturated aqueous solution, which implies losses, so make sure you have enough starting material (copper(II) salts) as well as a heating plate, preferably with a stirrer.

Synthesis from copper(II) carbonate

I doubt you have pure $\ce{CuCO3}$ because it cannot be obtained directly by exchange reactions in aqueous solutions between $\ce{Cu(II)}$ salts and soluble carbonates: due to hydrolysis you always get hydroxocarbonates $(\ce{Cu2(OH)2CO3}$ or $\ce{Cu3(OH)2(CO3)2}).$ Anyway, careful addition of sulfuric acid to either carbonate or hydroxocarbonate should yield in solution of copper(II) sulfate:

$$\ce{CuCO3(s) + H2SO4(aq) -> CuSO4(aq) + CO2(g) + H2O(l)}\tag{R1}$$

Synthesis from copper(II) acetate

Since both acetate and sulfate are readily soluble in water, you might need to remove acetate to facilitate crystallization of sulfate. This can be relatively laborious depending on how you can do this.

1. Convert acetate to insoluble copper(II) hydroxide by adding any water-soluble inorganic base (except, of course, ammonia):

   $$\ce{Cu(OAc)2(aq) + 2 NaOH(aq) -> Cu(OH)2(s) + 2 NaOAc(aq)}\tag{R2}$$

   The precipitate is usually quite amorphous and will be hard to filter. To make it more crystalline, try to warm up the solution a bit (do not exceed 80 °C) and then cool it down, say, in a fridge, to 4 °C. After decantation, washing the hydroxide from remaining acetate with deionized water on the filter and transferring it to a glass vessel, you can add sulfuric acid:

   $$\ce{Cu(OH)2(s) + H2SO4(aq) -> CuSO4(aq) + 2 H2O(l)} \tag{R3}$$

2. Alternatively, you may try to thermally decompose acetate to copper(II) oxide by heating it in the air above 300 °C:

   $$\ce{Cu(OAc)2(s) + 3 O2(g) ->[\Delta] CuO(s) + 3 H2O(g) + 2 CO2(g)} \tag{R4}$$

   Then, treat the cooled down oxide powder with the acid:

   $$\ce{CuO(s) + H2SO4(aq) -> CuSO4(aq) + H2O(l)} \tag{R5}$$

Note on inhibitors

Acid inhibitors are designed to prevent corrosion of construction materials such as carbon/stainless steel, aluminum and copper metals and alloys and should not affect the aforementioned reactions.