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Observe the following picture a write down the chemical reaction with explanation. ⇒ The picture given shows the corrosion of iron. ⇒ The chemical formula of rust is Fe2O3.H2O.

Question 15.

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



Answer:

⇒ The picture given shows the corrosion of iron.


⇒ The chemical formula of rust is Fe2O3.H2O.


⇒ The rust on iron does not form by a simple reaction of oxygen with iron surface. The rust is formed by an electrochemical reaction.


⇒ Different regions on the surface of iron become anode and cathode.


⇒ Fe is oxidised to Fe2+ (anode)


Fe (s) → Fe2+ (aq) + 2e-


⇒ O2 is reduced to form water (cathode)


O2 (g) + 4H+ (aq) + 4 e- → 2H2O


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


⇒ A redish coloured hydrated oxide is formed from Fe3+ ions.


⇒ It is called rust which collects on the surface.


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


⇒ Iron rusts and a redish coloured layer is collected on it.


⇒ This is corrosion of iron.