What is an electrochemical theory of rusting of irons and give two methods of preventing the rusting of iron?

Hint: The rusting of iron is a slow process in which the iron reacts with oxygen and forms an iron oxide which is usually reddish-brown in colour. We usually study the Nernst equation and the related numerical in electrochemistry.

Complete Step-by-Step Answer:
-According to the electrochemical theory of the rusting of iron, oxidation reaction occurs at anode and reduction reaction occurs at the cathode.
-At the anode, the iron is oxidised to the ferrous ions and the electrons which are released move towards the cathode.
At the anode: Fe (s) → Fe2+ + 2e−Fe (s) → Fe2+ + 2e−
-At the cathode, the hydrogen ions are taken from the moisture that is present in the atmosphere.
-So, the reaction of water releasing hydrogen ion is:

-At the cathode:

-But the oxygen that is present on the surface of the iron is reduced by hydrogen.iron rust remover So, the reaction becomes 4H+ + O2 +4e− → 2H2O4H+ + O2 +4e− → 2H2O
-Hence, by using the oxidation and reduction half-reaction we can write the overall reaction i.e.
2Fe + 4H+ + O2 → 2Fe2+ 2H2O2Fe + 4H+ + O2 → 2Fe2+ 2H2O
-This ferrous ion is further oxidized by the oxygen which forms rust:
4Fe2+ + O2 + 4H2O → 2FeO3 + 8H+4Fe2+ + O2 + 4H2O → 2FeO3 + 8H+
Two methods to prevent the rusting are:
-If we will paint (water-insoluble) the metal then it reduces the chances of rusting by separating the metal from the water.
-We can also use oil or grease to keep the water away from the iron.
Nernst Equation: The Nernst equation is the relation between the standard cell potential, temperature, cell potential of an electrochemical cell and the reaction quotient.
ECell = E∘Cell – 0.0592nlogQECell = E∘Cell – 0.0592nlog⁡Q
-Here, E∘CellE∘Cell is a standard electrode potential and log Q is the reaction quotient.
-To calculate the emf, we will use the formula of the Nernst equation:
ECell = E∘Cu2+/Cu + E∘Ni2+/Ni – 0.0592log(aNi2+aCu2+)ECell = 0.34V –(−0.22V) – 0.0592 log (0.010.01)ECell = 0.66VE���� = E∘Cu2+/Cu + E∘Ni2+/Ni – 0.0592log(aNi2+aCu2+)E���� = 0.34V -(−0.22V) – 0.0592 log (0.010.01)ECell = 0.66V

Therefore, the value of emf of the cell is 0.66V.

Note: The value of standard temperature is 298 Kelvin. Increase in the oxidation state means the oxidation whereas a decrease in the oxidation state means the reduction of a molecule. In the given question, nickel undergoes the oxidation reaction whereas copper undergoes the reduction reaction.