Question

How rsting of iron can be envisaged a setting up an electrochemical cell?

Answer 1

Solution:

In process of rusting, water molecules present at the layer of iron react with oxides and get dissociated and give H+ ions

 H2O + CO2    →        H2CO3

H2CO3                                ↔        2H+                 +          CO32–

In present of H+ ions iron convert in Fe2+ so this part is act as anode

Reaction at anode:

Fe(s)               →        Fe2+(aq)         +          2e–

Electron released at anodic spot move through the metals and go to another spot on the metal and reduce oxygen this spot act as cathode

Reaction at Cathode:

O2(g)   +  4H+(aq)  +  4e+( aq)          →        2H2O(l)


The overall reaction

2Fe(s)  + O2(g)    +    4H+(aq)          →        2H2O(l)  + Fe2+(aq)


Hence, rusting of iron act as electrochemical cell.