The Geochemical Reaction:
Ideas for Class Discussion

The chemical reaction that occurs when sulfuric acid is poured onto the oxidized copper ore (malachite) is as follows:

Cu₂CO₃(OH) ₂ + 2H₂SO₄---->2H₂O + 2CuSO₄ + H₂CO₃

In words, the reaction is

malachite + sulfuric acid ---->water + copper sulfate + carbonic acid

When a freshly sanded nail is dropped into the copper sulfate and carbonic acid solution, the ionized copper gains electrons from the nail to become native copper and preciptate onto the surface of the nail, as follows:

Fe + Cu²⁺----> Fe²⁺ + Cu

Ask students to think about how copper might be extracted from solution at a copper mine that uses a heap leaching process. One of the techniques that has been used is to precipitate the copper onto steel from used cars (copper cathode process). Numerous web sites treat the processes of mining and extracting copper, such as the online magazine for the Copper Development Association, known as Innovations (more info) .