Question

A black coloured substance is formed on the surface of copper metal when it is heated in oxygen in air. give reason.

Answer 1

The black coloured substance is copper oxide or CuO.

When oxygen which is present in the air starts to react with copper, a layer of copper oxide will be formed.

Eqn = 2Cu + 02 ----) 2CuO

Answer 2

A black-colored substance is formed on the surface of the copper metal when it is heated due to the formation of cupric oxide (CuO).

Here, we are talking about the oxidation reaction of copper metal. In this reaction, copper is heated in the presence of oxygen. The black-colored substance formed is copper oxide.

There are several oxides of copper, the one formed here is called cupric oxide with the formula CuO. In this compound, copper is in a +2 oxidation state and the color of cupric oxide is black.