Corrosion chemistry: When an iron nail rusts, which oxide compound is actually formed? Identify the specific iron oxide produced during rusting (under atmospheric moisture and oxygen). Choose the correct chemical name/formula.
General Knowledge
General Science
Difficulty: Easy
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Answer
Correct Answer: Hydrated ferric oxide (Fe₂O₃·nH₂O)
Explanation
Given data
- Metal: Iron (nail) exposed to air and moisture.
- Phenomenon: Rusting (electrochemical corrosion).
Concept/Approach Rust is not a single, simple oxide like FeO or Fe2O3. It is predominantly hydrated ferric oxide, commonly represented as Fe2O3·nH2O.
Reasoning • Moisture provides electrolyte → oxidation of Fe to Fe2+/Fe3+. • Oxygen reduces to hydroxide ions; hydrated ferric oxide forms and deposits as rust (reddish-brown).
Common pitfalls Confusing rust with magnetite (Fe3O4) or anhydrous Fe2O3; these may occur in scales but typical atmospheric rust is hydrated ferric oxide.
Final Answer Hydrated ferric oxide (Fe₂O₃·nH₂O)