Acids that dissolve copper:
* Nitric Acid (HNO₃): This is the most common and effective acid for dissolving copper. The reaction produces copper(II) nitrate, nitrogen dioxide gas (a reddish-brown gas), and water:
```
Cu(s) + 4HNO₃(aq) → Cu(NO₃)₂(aq) + 2NO₂(g) + 2H₂O(l)
```
* Hot Concentrated Sulfuric Acid (H₂SO₄): This reaction is slow but will dissolve copper. It produces copper(II) sulfate, sulfur dioxide gas, and water:
```
Cu(s) + 2H₂SO₄(conc.) → CuSO₄(aq) + SO₂(g) + 2H₂O(l)
```
Why these acids work:
* Oxidation: Copper is a relatively unreactive metal, but it can be oxidized by strong oxidizing agents like nitric acid and hot concentrated sulfuric acid. These acids act as oxidizers, removing electrons from copper atoms and forming copper ions (Cu²⁺).
* Formation of Soluble Salts: The copper ions then react with the anions from the acid to form soluble salts. These salts, like copper(II) nitrate and copper(II) sulfate, dissolve in the acidic solution.
Acids that do NOT dissolve copper:
* Hydrochloric Acid (HCl): While HCl is a strong acid, it is not a strong oxidizing agent. Therefore, it cannot oxidize copper to form copper ions.
Important Note:
* The reactions of copper with acids are exothermic and can produce toxic fumes. Always handle these reactions with appropriate safety precautions, including a fume hood and protective gear.
