A copper statue was found to lose its lustre after some time. a layer of a dull green coating was deposited over it . explain the cause along with a relevant word equation.
Answers
The greenish layer which appears on the surface of Copper if actually the corrosion of Copper. Copper firsts reacts with Oxygen to form Copper Oxide(CuO). Further this Copper Oxide reacts with Carbon dioxide to form Copper carbonate(CuCO3).
2Cu + O2 ―> 2CuO
CuO + CO2 ―> CuCO3
Statue of Liberty is an example of corrosion of Copper. When France gifted America The Statue of Liberty it was brown in colour but gradually it turned green.
Copper can also be corroded by acid rain. When Carbon dioxide reacts with rainwater it forms Carbonic acid(H2CO3) which reacts with Copper to form Copper carbonate. This is the way in which Statue of Liberty is corroded.
Cu + H2CO3 ―> CuCO3 +H2
Hope it helps!!!
Thanks.
The copper statue was found to lose its lustre after some time because of its exposure to the environment (atmospheric O2 and CO2 and moisture).
2Cu(s) + H2O(g)+CO2(g)+O2(g)→ Cu(OH)2(S) +Cu(CO)3 (s)