Question

With the help of a labelled diagram prove by an experiment that both oxygen/air and water are necessary for rusting of iron.

Answer 1

Corrosion of any metal is a natural process. It results in the conversion of the metal into its chemically stable form that can be either oxides or hydroxides or sulphides. Rusting is a type of Chemical Change. It results in the formation of Iron Oxide which is an entirely new substance. Chemical Reaction of Rusting is as follows:
Iron + Oxygen (from the environment) + Water (Humidity) —> Iron Oxide (Rust)

$Fe$ + $O_2$ + $H_{2}O$ —> $FeO$ and $F{e}_2{O}_3$

In the given figure, rusting of iron takes place only in presence of oxygen and water vapours. In figure (c) rusting is not possible as the supply of oxygen is blocked by the oil layer.