What is the valency of iron in the products formed
(a) When iron is exposed to humid air for a long time?
(b) When red hot iron is made to react with steam?

Explanation

When Fe is exposed to humid air for a long period of time, it gets rusted.
Rust: `Fe_2O_3 xx H_2O`
Valency of Fe is 3.
Valency of Fe is 3
(b) `underset("Steam")(3Fe) + underset("(Ferroso-ferric oxide)")(4H_2O to Fe_3O_4 + 4H_2)`
(`Fe_3O_4` is mixed oxide, i.e., `FeO + Fe_2O_3`)
(valency of iron in Fe3O4 is 2 as well as 3)