Reduction of copper. Copper oxide (CuO) heated in a test tube with zinc (Zn). The use of the zinc, which is more reactive than copper, leads to the formation of zinc oxide (ZnO) and copper (Cu). The copper is reduced from the oxide to the metal. This has varied applications, from the use of zinc to prevent corrosion of copper, to the extraction of copper from its oxide ores. This displacement of copper by zinc is normally carried out in an aqueous solution. Here, additional reactions can complicate matters, such as the formation of the zinc-copper alloy called brass. The equation for the displacement reaction is: CuO + Zn -> ZnO + Cu