A piece of copper metal is heated in a flame and oxidized to black copper oxide by air. The oxidized copper is reduced when placed in a hydrogen atmosphere. When removed from the hydrogen atmosphere, the metal is again oxidized.
Discussion:
Copper oxidizes slowly in air, corroding to produce a brown or green patina. At higher temperatures the process is much faster and produces mainly black copper oxide. The oxide can be reduced by hydrogen gas, which is a moderately strong reducing agent, producing a shiny, clean copper surface. This provides a striking illustration of oxidation and reduction of a metal.
Equations for the reactions are
2 Cu(s) + O2(g) —> 2 CuO(s)
CuO(s) + H2(g) —> Cu(s) + H2O(g)
Credits:
- Demonstration
- John W. Moore University of Wisconsin - Madison, Madison, WI 53706
- Setup
- Lynn R. Hunsberger University of Louisville, Louisville, KY 40292
- Video
- Steven D. Gammon University of Idaho, Moscow, ID 83843
- Text
- Kelly Houston Jetzer University of Wisconsin - Madison, Madison, WI 53706
- John W. Moore University of Wisconsin - Madison, Madison, WI 53706