The question of how vinegar + hydrogen peroxide + table salt can be used to etch copper has been asked before (Full equation when using vinegar, hydrogen peroxide, and salt to etch copper). However, the accepted answer seems to miss a key fact when observing this reaction, so I wanted to ask for clarification in the hope that someone can explain the unaddressed fact.

When the vinegar + hydrogen peroxide + table salt solution is used to etch copper, there is a gas that vigorously forms on the surface being etched. However, none of the reaction products in the accepted answer for the full equation for this reaction are volatile. So if none of the reaction products are volatile, how can a gas be released? Clearly, there is something missing from the accepted answer. Does anyone have any ideas?

  • $\begingroup$ Make a bold guess! ;) $\endgroup$ – Karl Jan 13 '20 at 20:34
  • $\begingroup$ My guess would be hydrogen, but if so, the accepted equation for this reaction is wrong, so I am hoping someone can address both points at once. $\endgroup$ – Marc Sulfridge Jan 13 '20 at 20:38
  • $\begingroup$ OK, it´s not hydrogen. Hydrogen evolves when base metals react with water (or acid). Next guess, please. (The accepted answer of that other question is correct as far as I see, but it does in fact not tell you what gas comes out. There is another reaction.) $\endgroup$ – Karl Jan 13 '20 at 20:46
  • $\begingroup$ OK, so it is probably oxygen, then. So what is the missing link in the reaction process? $\endgroup$ – Marc Sulfridge Jan 13 '20 at 20:52
  • $\begingroup$ Correct. The point is that you add a rather large excess of peroxide. It just bubbles away. $\endgroup$ – Karl Jan 13 '20 at 21:01

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