Question

1 g of copper powder was in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the color of the formed is each case.

Answer 1

•  When the “copper powder” is heated in a ‘china dish’, the copper powder surface becomes coated with “black colour substance” due to the formation of ‘copper oxide’ by surface oxidation. 

• Copper reacts with oxygen in the air upon heating and forms copper oxide. The black colour is due to the formation of this copper (II) oxide. 

•  The copper oxide thus formed can be reduced to its basic metal form by reducing it with hydrogen or carbon monoxide. 

The equation of ‘copper (II) oxide’ formation is: 

2Cu + O₂ → 2CuO