Question

What is the half-reaction for the reduction of oxygen that occurs with the corrosion of iron? Using this reaction, explain why corrosion occurs more slowly in dry climates.

Answer 1

corrosion is the rusting of iron 
formation requires iron, oxygen, water

4Fe(s) + 3O2(g) + 2H2O(l) --> 4FeO(OH) 

Clearly, without water, there would be no formation of rust. 

Redox half-reactions: 
Fe(s) + 2H2O --> FeO(OH)(s) + 3H+ + 3e- .... oxidation of iron 
3(Fe(s) + O2 + H+ + 1e- --> FeO(OH)) .......... reduction of oxygen 
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4Fe(s) + 3O2 + 2H2O --> 2FeO(OH) ....... H+ cancels out, e- cancels out