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

The shiny brown coloured element ‘X’ is copper (Cu).
When copper is heated in air, it reacts with oxygen to form a black coloured compound called copper(II) oxide (CuO).

Reaction:
Cu + O₂ → 2CuO

Explanation:

  • Copper (Cu), which is shiny and brown, reacts with oxygen in the air when heated.
  • This forms copper(II) oxide (CuO), which is black in colour.
  • The surface of the copper turns black due to the formation of this oxide layer.

Answer Summary:

  • Element X: Copper (Cu)
  • Black compound formed: Copper(II) oxide (CuO)
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