What is copper?

What dissolves copper?

• acids seem to clean copper more than dissolve it. i wanted to make copper sulfate crystals and some other pretty colored copper crystals, but acids seem to clean the copper more than combine with it. i know copper is low on the reactivity list, but it does become oxidized. can i turn it into any form of copper salt easily and then change that salt into the desired crystal?

• Answer:

  This is a standard experiment in many college teaching labs. Sulfuric acid reacts very slowly with copper so making copper(II) sulfate directly is not going to work. However, copper reacts very quickly with nitric acid (an oxidizing acid). Copper(II) sulfate (actually pentahydrate) is much less soluble than copper(II) nitrate. Therefore adding sulfuric acid to the copper(II) nitrate will yield (by anion exchange) the copper(II) sulfate. Cooling (and/or concentrating) the solution will precipitate the copper(II) sulfate pentahydrate. If you try this, you should be aware of safety issues. The nitric acid/copper reaction produces a toxic, gaseous byproduct. This reaction requires fairly concentrated nitric and sulfuric acids. As Ira Remsen is famous for saying, " I learned another fact--nitric acid not only acts upon copper but it acts upon fingers. The pain led to another unpremeditated experiment. I drew my fingers across my trousers and another fact was discovered. Nitric acid acts upon trousers." Sulfuric acid will do as much or worse to your skin and clothes as nitric acid will.