Question

Draw the process of the rusting of iron and note the 4-5 chemical ½ reactions. How do we prevent rusting?

Answer 1

Rusting is an electro chemical phenomenon .

In this process Iron reacts with air and moisture and forms hydrated ferric oxide whis is usually called Rust.(flaky,reddish brown solid on iron articles)

Process:Rusing is a redox reaction also termed as corrosion.

It invoves the following steps

step1:Oxidation half reaction: Fe(s) → Fe²⁺(aq) + 2e- (iron (Fe) is oxidised to Fe²⁺ ions )

step2:Reduction half reaction: O₂(g) + 2H₂O(l) + 4e- → 4OH-(aq)(Oxygen is reduced to hydroxyl ions)

Redox Reaction:2Fe(s) + O₂(g) + 2H₂O(1) → 2Fe²⁺(aq) + 4OH-(aq) (Balanced reaction of the above equations) Two iron atoms are oxidised for every one oxygen molecule reduced)

step3:Fe²⁺(aq) + 2OH-(aq) → Fe(OH)₂(s) (here Fe²⁺ions reacted with OH^- ions to form Ferrous hydroxide which is never observed) so again it reacts with Oxygen to form hydrated Ferric Oxide usually appears in reddish brown colour called Rust.

step4:4Fe(OH)₂(s) + O₂(g) + xH₂O(I)→ 2Fe₂O₃•(x+4)H₂O(s) Rust

Preventing steps: Applying Oil or grease on iron articles

Coating of Zinc on Iron using electrochemical process(Galvanisation)

Applying paint on iron

In all the above cases the outer surface protects the underneath Iron surface from oxidation-Reduction process.