ICSE Class 7 Answered

Dear Student,

Iron rusting is the result of oxidation. Iron does not rust due to a straightforward reaction between oxygen and the iron's surface. Rust is produced through an electrochemical process. On one portion of the iron surface, Fe oxidizes to Fe₂O₃.H₂O, whereas on another, oxygen is reduced to H₂O.

Different areas of the iron's surface take on the roles of cathode and anode.

(1) Fe is oxidised to Fe²⁺ in the anode region:

Fe(s) → Fe²⁺ (aq) + 2e^–

(2) O₂ is reduced to form water in the cathode region:

O₂(g) + 4H⁺ (aq) + 4e⁻ → 2H₂O(l)

When Fe²⁺ ions migrate from the anode region, they react with water and further get oxidised to form Fe³⁺ ions.

A reddish coloured hydrated oxide is formed from Fe³⁺ ions which is called rust. It collects on the surface.

2Fe³⁺ (aq) + 4H₂O(l) → Fe₂O₃. H₂O(s) + 6H⁺(aq)

Due to various components in the atmosphere, oxidation of metals takes place resulting in their damage. This is called ‘corrosion’.

Iron rusts and a reddish-coloured layer is formed on it. This is corrosion of iron which is termed as rusting.