Question

Q.corrosion is essentially an electrochemical phenomenon.Explain the reaction occuring during corrosion of iron kept in an open atmosphere.

Answer 1

hey friend hope this will help you
➡️when iron metal is kept in air it react with oxygen present in air in presence of moisture to form surface compound
this surface ciompound formed by the oxidation of iron is called rust

Answer 2

Hey !!

According to electrochemical theory of rusting the impure iron surface behaves like small electrochemical cell in the presence of water containing dissolved oxygen or carbon dioxide. In this cell pure iron acts as anode and impure iron surface acts as cathode. Moisture having dissolved CO₂ or O₂ acts as an electrolyte.

The reaction are given below.

At anode :- Fe -------> Fe²⁺ + 2e⁻ ; E°fe²⁺/Fe = - 0.44 V

At cathode :- 2H⁺ + 1/2O₂ + 2e⁻ -------> H₂O ; E°H⁺/O₂/H₂O = 1.23 V

Overall reaction :_ Fe + 2H⁺ + 1/2O₂ -------> Fe²⁺ + H₂O ; E°cell = 1.67 V

The Fe²⁺ ions are further oxidised by atmospheric oxygen to Fe³⁺ ions, which comes out in the form of hydrated ferric oxide (rust)

              2Fe²⁺ + 1/2O₂ + 2H₂O ------> Fe₂O₃ + 4H⁺

              Fe₂O₃ + xH₂O -------> Fe₂O₃ . xH₂O (RUST)

Hope it helps you !!