why colour of a] iron become raddish 
                     b] silver become blackish
                      c]copper become green 
when exposed in atmosphere for longer period of time
write answer in form of chemical equation

Asked by ambikesh singh | 5th Jun, 2014, 08:41: PM

Expert Answer:

a) Iron when comes in contact with moist air reacts to give rust which is a brown powder mainly hydrated iron(III)oxide(Fe2O3 .xH2O).
4Fe + 3O2 + 2xH2O → 2Fe2O3 .xH2O
b) Silver gets tarnished when exposed to the atmosphere which contains pollutant H2S and forms a black coating of Ag2S.

2Ag(s) + H2S(g) → Ag2S(s) + H2(g)

c) Copper forms a green deposit on its surface when exposed to moist air. This is usually basic copper(II)sulphate[3Cu(OH)2.CuSO4].

Answered by Vaibhav Chavan | 9th Jun, 2014, 11:08: AM

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