Question

Statue of liberty, though made of copper, it is covered with a dull green coating. What are the compounds present in that coating? Write necessary chemical reaction taking place in this case.

Answer 1

Explanation:

It is due to corrosion of copper whereby the formation of basic copper carbonate takes place which is green in colour.

The green material is a mixture of copper hydroxide (Cu(OH)2) and copper carbonate (CuCO3). The following is the reaction:

2Cu(s)+H2O(g)+CO2+O2→Cu(OH)2+CuCO3(s)

Answer 2

Answer:

It's not a simple single reaction between copper and oxygen to produce a green oxide.The copper oxide continues to react to make copper carbonates, copper sulfide, and copper sulfate.

There are three main compounds that form the blue-green patina: 

Cu4SO4(OH)6 (green)

Cu2CO3(OH)2 (green)

Cu3(CO3)2(OH)2 (blue)

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