When a copper vessel is exposed to moist air for long, it acquires a dull green coating. The reaction can be represented as
W, X, Y and Z are respectively
AN2, CO2, O2 and CuO
BH2O, N2, CO2 and O2
CH2O, CO2, O2 and CuCO3
DH2O, CO2, O2 and CuO.