Question

Observe the following picture a write down the chemical reaction with the explanation.

Answer 1

The rusting of iron is an oxidation process. The rust on iron does not form by a simple reaction between oxygen and iron surface. The rust is formed by an electrochemical reaction. 'Fe' oxidises to Fe₂O₃.XH₂O (Rust) is on one part of the iron surface, while oxygen gets reduced to H₂O in another part of the surface. Different regions on the surface of iron become anode and cathode.

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

\[\ce{Fe(s) -> Fe^{2+}(aq) + 2e^-}\]

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

\[\ce{O2(g) + 4H^+(aq) + 4e^- -> 2H2O(l)}\]

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. It is called rust. It collects on the surface.

\[\ce{2Fe^{3+}(aq) + 4H2O(l) -> Fe2O3.H2O(s) + 6H^+(aq)}\]

Due to various components of the atmosphere, oxidation of metals takes place, consequently resulting in their damage. This is called 'corrosion'. Iron rusts, and a reddish-coloured layer is collected on it. This is the corrosion of iron.