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Question
Write a chemical equation to show the process of corrosion of iron.
Solution
In corrosion, oxidation of iron takes place.
Fe (s) → Fe2+ (aq) + 2e−
Iron supplies electrons at the edge of the droplet to reduce oxygen from the air.
O2 (g) + 2H2O (l) + 4e− → 4OH− (aq)
Within the droplet, the hydroxide ions react with the iron(II) ions and iron(II) hydroxide is precipitated.
Fe2+ (aq) + 2OH− (aq) → Fe(OH)2 (s)
Rust is then quickly produced by the oxidation of the precipitate.
4Fe(OH)2 (s) + O2 (g) → 2Fe2O3 • H2O (s) + 2H2O (l)
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