2
$\begingroup$

I made a solution of copper acetate using 5% Acetic acid 3%hydrogen peroxide and copper wire and copper pipe and it had produced a blue solution of copper acetate. I left it over night to continue reacting, but when I came back In the morning the solution turned clear. I didn’t do any Stoichiometry so I don’t know if they’re was a excess of H2O2 or a excess of acetic acid. I’m wondering if you know what happened

$\endgroup$
4
  • 1
    $\begingroup$ Was a precipitate created? $\endgroup$ – AJKOER May 2 '20 at 0:41
  • $\begingroup$ Was anything precipitated? Corrosion on the pipe? $\endgroup$ – Oscar Lanzi May 2 '20 at 0:43
  • $\begingroup$ I am asking again whether any precipitate was created and whether any testing was done on samples. Disagreement has emerged in the answers and we need more experimental evidence to resolve it. $\endgroup$ – Oscar Lanzi May 3 '20 at 12:05
  • 1
    $\begingroup$ No there is no precipitate and after sitting for a few days nothing has changed, and I may continue testing. $\endgroup$ – 15year old chemist May 5 '20 at 5:20
2
$\begingroup$

Wikipedia states that upon heating, copper(II) acetate reacts with metallic copper to make copper(I) acetate, which would be colorless. While this is no guarantee of what happened with your solution, you can mix a sample of the solution with saltwater (chloride ions). White precipitate = copper(I).

In light of a comment, I am compelled to expand on the possibility of copper(I) in solution. According to the Wiley Online Library, this salt is soluble in water with hydrolysis to cuprous oxide. At the same time we have the copper Pourbaix diagram reported from Ref. 1, indicating that the oxide is stable only above a pH of 4.

enter image description here

This means any significant leftover acetic acid could prevent the hydrolysis and keep the copper(I) in solution, apparently stabilized by complexing with the acetate ion given that disproportionation is not reported. (Such a stabilization is not included in the above diagram but would contract the Cu2O region further.)

Since this is only indirect evidence, again testing for a copper(I) chloride precipitate by mixing a sample with saltwater is recommended.

Reference

1. Oh, Youn-Jin & Park, Gyung-Soon & Chung, Chan-Hwa. (2006). Planarization of Copper Layer for Damascene Interconnection by Electrochemical Polishing in Alkali-Based Solution. Journal of The Electrochemical Society - J ELECTROCHEM SOC. 153. 10.1149/1.2200288.

$\endgroup$
6
  • $\begingroup$ In the presence of H2O2, Cu(I) cannot survive, assuming there is some residual H2O2. $\endgroup$ – M. Farooq May 2 '20 at 2:13
  • $\begingroup$ Is there a way to reverse this $\endgroup$ – 15year old chemist May 2 '20 at 5:03
  • $\begingroup$ @mfarooq right, but we don't know if h2o2 would be present. It may not survive itself with the copper pipe. $\endgroup$ – Oscar Lanzi May 2 '20 at 8:39
  • $\begingroup$ @15 I would test for the reduction to copper(i) before pursuing any sort of recovery. Let us know what happened if you run the suggested test. $\endgroup$ – Oscar Lanzi May 2 '20 at 8:44
  • $\begingroup$ The reaction is Cu + Cu(II) <--> 2 Cu(I) and is an equilibrium reaction, so this should not be an explanation as to how the solution becomes colorless. $\endgroup$ – AJKOER May 3 '20 at 3:37
0
$\begingroup$

A reaction equilibrium is established between Copper metal and Cuprous in acetic acid and H2O2:

$\ce{Cu + Cu(II) (aq) <=> Cu(I) (complex)}$

where I assume that initially, the cuprous acetate is soluble in excess acetic acid, forming a so-called acid salt. As such, the coloration of the solution is maintained due to reaction the equilibrium.

However, in time, with excess H2O2 and acetic acid acting on Copper metal, the acetic acid is likely consumed. This now results in the reaction:

$\ce{Cu + Cu(II) (aq) -> Cu(I) (s)}$

where now an insoluble cuprous acetate is formed, resulting in a clear solution also containing a clear cuprous acetate crystal precipitate.

$\endgroup$
1
  • $\begingroup$ This also may not really work. Wiley Online Library lists cuprous acetate as soluble in water with hydrolysis to cuprous (not cupric) oxide, so either you get the precipitated oxide or, with remaining acetic acid to suppress the hydrolysis, it remains in solution. If you read carefully you will see that I had recommended testing for copper(I), not said definitely it was there. $\endgroup$ – Oscar Lanzi May 3 '20 at 9:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.