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There's an experiment I have no way of performing but want to know its results. The instructions (in short) are:

Dip a piece of copper in a glass of concentrated nitric acid, $\ce{HNO3}$, using a pincette. When a brown gas starts forming, take out the piece of copper and rinse it with water. Right after that dip it into $\ce{HgNO3}$ solution. Leave it in there for some time and then take it out of the solution. Rinse it with water and wipe it with a napkin.

How does the piece of copper look?

What I've worked out is that the first part can be written as: $$\ce{Cu (s) + 4HNO3 (aq) -> Cu(NO3)2 (aq) + 2NO2 (g) + 2H2O(l)}$$ and that $\ce{NO2}$ is the brown gas.

What I'm not sure about is why exactly I'm dipping the copper piece into a solution of $\ce{HgNO3}$ following the above reaction. And why am I rinsing it with water before dipping it into the $\ce{HgNO3}$ solution?

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  • $\begingroup$ @student States of aggregation should not be subscripted, it is not wrong, but the recommendations (Sec. 2.1.) are different. $\endgroup$
    – Martin - マーチン ♦
    May 12, 2016 at 5:30
  • $\begingroup$ @Martin-マーチン Thank you, will bear it in mind. $\endgroup$
    – user25546
    May 14, 2016 at 7:22

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Metals often have corrosion on their surface, such as oxides. By dipping in nitric acid and then rinsing with water you would achieve a true copper metal surface free of oxide or other corrosion products.

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You will likely be creating a mercury-copper amalgam similar to this

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