Question

You might have noted that when copper powder is heated in a china dish,the surface of Copper powder becomes coated with a black colour substance. i)How has this black coloured substance formed? ii)What is the black substance? iii)Write the chemical equation of the reaction that takes place.

Answer 1

1. When the copper is heated with oxygen copper oxide which is the black colour substance is formed.
2.The black colour substance is CuO
3.The reaction is
2Cu + 02 =2 CuO

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Answer 2

Answer: 1) By Oxidation of copper powder

2) $CuO$

3) $2Cu+O_2\rightarrow 2CuO$

Explanation: When copper is heated in a china dish, it reacts with atmospheric oxygen and thus undergo oxidation leading to formation of copper oxide $CuO$ which is black in color.

$2Cu+O_2\rightarrow 2CuO$

This is an example of redox reaction in which copper undergoes oxidation that is it loses electron and oxygen undergoes reduction in which it gains electrons.

Oxidation: $Cu\rightarrow Cu^{2+}+2e^-$

Reduction: $\frac{1}{2}O_2+2e^-\rightarrow O^{2-}$