Question

A shiny brown colored element ‘X’ on heating in the air becomes black in color. Name the element ‘X’ and the black colored compound formed.

Answer 1

Reaction of Copper with air:

1. Copper ($\mathrm{Cu}$) is actually a chemical element with atomic number 29.
2. It is actually a native element which occurs in the nature in the pure form.
3. Copper is actually brown in color and also on reaction with oxygen it forms Copper oxide which is black in color.
4. So basically, when Copper metal is heated in air.
5. It will get oxidized for the formation of Copper oxide which is black in color.
6. This all is actually a redox reaction in which the Copper is oxidized to Copper oxide and so the Oxygen is reduced.
7. Reaction: $\underset{\mathrm{Copper}}{2\mathrm{Cu}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Copper}\mathrm{oxide}}{2\mathrm{CuO}\left(\mathrm{s}\right)}$.

Therefore, A shiny brown element ‘X’ which on heating in air becomes black in color is basically Copper element and black colored compound formed is Copper oxide.