The correct sequence of steps during the corrosion of iron is

(A) Ferrous ions are oxidized by atmospheric oxygen
(B) Hydrated ferric oxide $(FeO_3.xH_2O)$ formed with production of $H^+$ ions
(C) At a particular spot of iron object, oxidation takes place and that spot behaves as anode
(D) Electron released at anode moves through metal and reduces oxygen in the presence of $H^+$

Choose the correct answer from the options given below:

(C), (D), (A), (B)

The correct answer is Option (4) → (C), (D), (A), (B)

Corrosion of iron (rusting) is an electrochemical process that occurs in the presence of moisture and oxygen. The process involves oxidation at the anode and reduction at the cathode.

Step 1: Formation of anodic region

At certain spots on the iron surface, oxidation occurs. Fe → Fe²⁺ + 2e⁻

These regions behave as anodes. Thus, (C) occurs first.

STep 2: Reduction of oxygen

The electrons released at the anode move through the metal to another region where oxygen is reduced.

O₂ + 4H⁺ + 4e⁻ → 2H₂O Thus, (D) occurs next.

Step 3: Oxidation of ferrous ions

The ferrous ions formed are further oxidized by atmospheric oxygen to ferric ions. Thus, (A) occurs next.

Step 4: Formation of rust

Ferric ions combine with water to form hydrated ferric oxide, commonly called rust. Fe₂O₃ · xH₂O

Thus, (B) occurs last.