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JAMB Chemistry 2011 Paper

Question : 24

Total: 47

The condition required for corrosion to take place is the presence of

Solution:

Concept:

Corrosion of iron (rusting) requires both moisture and oxygen.

Explanation:

For corrosion to occur, iron is oxidised by oxygen in the presence of water:

\mathrm{Fe} \rightarrow \mathrm{Fe}^{2+} + 2e^-

and oxygen is reduced:

\mathrm{O}_2 + 2\mathrm{H}_2\mathrm{O} + 4e^- \rightarrow 4\mathrm{OH}^-

Thus, the essential conditions are water and oxygen.

Carbon (IV) oxide is not a necessary condition.

Answer:

D. water and oxygen

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