Question

4. Which of these statements is true of the rusting of iron?

• A. It requires oxygen and sulphur
• B. It requires moist air and sulphur
• C. It requires moisture and oxygen
• D. It requires calcium oxide

Answer 1

The correct option is C

It requires moisture and oxygen

Explanation:

(C)

• Rusting of iron refers to the formation of rust, a mixture of iron oxides, on the surface of iron objects or structures.
• This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high levels of moisture).
• The rusting of iron is characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder.
• This phenomenon is a great example of the corrosion of metals, where the surfaces of metals are degraded into more chemically stable oxides.
• The reaction is as follows: $\underset{\mathrm{Iron}}{4\mathrm{Fe}}+\underset{\mathrm{Oxygen}}{2{\mathrm{O}}_2\stackrel{{\mathrm{xH}}_2\mathrm{O}}{\to }}\underset{\mathrm{Iron}\left(\mathrm{III}\right)\mathrm{oxide}}{2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}}$

Conclusion: Thus option (C) is the correct answer.