State reasons for the following, ''Rusting of iron is said to be an electrochemical phenomenon.''

Explanation

The mechanism of rusting is explained with the help of electro-chemical theory.
This is because, it involves the formation of small electro-chemical cells on the surface of iron. In fact, the drops of water containing dissolved `O_(2) and CO_(2)` get attached on the rough surface of iron. They lead to the formation of electrolytic solution. Here, oxidation-reduction reaction takes place.
The rusting of iron is shown in the given fiure :
At anode : Fe undergoes oxidation as follows : `Fe(s)rarrFe^(2+)(aq)+2e^(-)`
At cathode: Carbonic acid is formed by the combination of `CO_(2) and H_(2)O`.
`H_(2)O+CO_(2)iffunderset("carbonic acid")(H_(2)CO_(3))`
`H_(2)CO_(3)iff2H^(+)+CO_(3)^(2-),H_(2)OiffH^(+)+OH^(-)`

These `H^(+)` ions accept the electrons as follows : `H^(+)+e^(-)rarrH`
The hydrogen atom combines with oxygen dissolved in water or present in air. It leads to form `H_(2)O` molecule. `4H+O_(2)rarr2H_(2)O`. The `Fe^(2+)` ions react with oxygen and water and ferric oxide is formed. `4Fe^(2+)(aq)+4H_(2)O+O_(2)rarr2Fe_(2)O_(3)+8H^(+)(aq)`
Ferric oxide combines with water to form hydrated ferric oxide. `Fe_(2)O_(3)+xunderset("Rust")(H_(2)O)rarrFe_(2)O_(3)xH_(2)O`