Question

On heating copper powder in air, the surface of copper powder becomes coated with black CuO. How can this black coating be converted into brown copper ? Write chemical equation for the reaction that occurs during the colour change.

Answer 1

Hydrogen gas is passed through the black copper oxide and as a result, it gets reduced to copper which is brown in colour.
`underset("(Black)")(CuO) + H_(2) to underset("(Brown)")(Cu) + H_(2)O`