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.
