. Copper becomes green when exposed to moist air for


a long period of time due to the

A: formation of a layer of cupric oxide on the surface of copper.

B: formation of a layer of basic carbonate of copper on the surface of copper.

C: formation of a layer of cupric hydroxide on the surface of copper.

D: none of the above.

 

 

Best Answer

Explanation:

Copper metal becomes green when exposed to moist air for a long period of time. This is because when copper metal is exposed to air, it reacts with different gasses and and moisture in the air.

Especially during monsoons, when the moisture in air is high, the copper metal reacts with water, oxygen and carbon dioxide from air to give different products.

2Cu+H2O+CO2+O2 Cu(OH)2+CuCO3

It is due to these reactions that copper gets corroded and coated with a mixture of copper carbonate (CuCO3) and copper hydroxide (Cu(OH)2).

The mixture of carbonate and hydroxide is referred to as basic carbonate. 

The basic carbonate of copper is green in colour and hence, it is because of the formation of basic carbonate of copper that the copper surface turns green with time.

Final Answer:

Hence, the correct answer is option B: formation of a layer of basic carbonate of copper on the surface of copper.

 

 

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