Question

Copper becomes green when exposed to moist air for a long period. This is due to ______

Options

• the formation of a layer of cupric oxide on the surface of copper.

• the formation of a layer of basic carbonate of copper on the surface of copper.

• the formation of a layer of cupric hydroxide on the surface of copper.

• the formation of a basic copper sulphate layer on the surface of the metal.

Answer 1

Copper becomes green when exposed to moist air for a long period. This is due to the formation of a layer of basic carbonate of copper on the surface of copper.

Explanation:

When copper is exposed to moist air containing CO₂, it develops a thin, green layer of the basic carbonate CuCO₃·Cu(OH)₂.