Question

Identify the type of chemical reaction taking place and also write the balanced chemical equation for: On heating copper powder in the air in a china dish, the surface of copper powder turns black.

Answer 1

Hint: Heating of copper powder is an oxidation reaction. Oxidation reactions are where oxygens are added or removal of hydrogen. It can also be defined as loss of electrons.

Complete step by step answer: On heating copper powder in the air in a china dish, the surface of copper powder turns black or gets coated with a black colour substance due to formation of copper oxide. The chemical reaction taking place is known as surface oxidation. It can be expressed as follows:
\[{\text{2C}}{{\text{u}}_{{\text{(s)}}}}{\text{ + }}{{\text{O}}_{{\text{2(g)}}}} \to {\text{2Cu}}{{\text{O}}_{{\text{(s)}}}}\]
The above chemical equation is a balanced equation.
So, what happens here is that oxygen present in the air attacks the copper to form copper oxide (CuO). The oxidation state of copper is +2 in this case.
The formed copper oxide can be reduced back to its metal form by reduction process. This can take place when copper oxide reacts with hydrogen or carbon monoxide.
The chemical reaction that is taking place on heating copper powder in the air in a china dish is an oxidation reaction that leads to the copper surface turning into black.

Note: During the heating of copper powder only oxidation takes place since black colour on the surface of copper is obtained. There is a possibility for the copper to get in metal form which is known as reduction. When simultaneous oxidation and reduction occurs, they are known as redox reactions.