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

Answer:

Copper is the metallic element with a gleaming brown sheen to it (Cu). When copper is heated in the presence of oxygen, copper oxide is formed as a result of the reaction with the oxygen in the air. Thus, the copper oxide is a dark-colored compound with a black appearance.

2Cu(s) + O₂(g) → 2CuO(s)