Q. Corrosion of iron is essentially an electrochemical phenomenon where the cell reactions are
A) Fe is oxidised to ${Fe}^{2 +}$ and dissolved oxugen in water is reduced to ${OH}^{-}$
B) Fe is oxidised to ${Fe}^{3 +}$ and $H_{2}O$ is reduced to $O_{2}^{2 -}$
C) Fe is oxidised to ${Fe}^{2 +}$ and $H_{2}O$ is reduced
to $O_{2}^{-}$
D) Fe is oxidised to ${Fe}^{2 +}$ and $H_{2}O$ is reduced
to $O_{2}$
Explanation
(a)
Fe → ${Fe}^{2 +} + \ {2e}^{-}$ (anode reaction)
$O_{2} + \ {2H}_{2}O$ + ${4e}^{-}\ \longrightarrow \ {4OH}^{-}$ (cathode reaction)
The overall reaction is
2Fe + $O_{2} + \ {2H}_{2}O$ → 2Fe($O{H)}_{2}$
Fe($O{H)}_{2}$ may be dehydrated to iron oxide FeO, or further oxidized to Fe($O{H)}_{3}$ and then dehydrated to iron rust, ${Fe}_{2}O_{3}.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.