Question
When iron reacts with dilute nitric acid. Iron (II) nitrate forms at first but gets changed to iron(III) nitrate. What colour changes occur?
Is dilute nitric acid an oxidizing agent or a reducing agent? Briefly Explain. Write an overall equation to explain these results.
Is dilute nitric acid an oxidizing agent or a reducing agent? Briefly Explain. Write an overall equation to explain these results.
Answers
Answered by
GPT-5 mini
Observations
- At first the solution is pale green (characteristic of Fe2+).
- It soon turns yellowish to brown as Fe2+ is oxidized to Fe3+ (and brown NO2 fumes may be seen).
Oxidizing/reducing role
- Dilute HNO3 acts as an oxidizing agent. Nitrate (NO3–) oxidizes iron (Fe → Fe3+) and itself is reduced (typically to NO under these conditions).
Half‑reactions (brief)
- Oxidation: Fe → Fe3+ + 3 e–
- Reduction: NO3– + 4 H+ + 3 e– → NO + 2 H2O
Overall balanced equation
Fe + 4 HNO3 → Fe(NO3)3 + NO + 2 H2O
This shows iron is oxidized to Fe3+ (yellow/brown solution) while nitrate is reduced to NO (sometimes observed as brown NO2 after oxidation in air).
- At first the solution is pale green (characteristic of Fe2+).
- It soon turns yellowish to brown as Fe2+ is oxidized to Fe3+ (and brown NO2 fumes may be seen).
Oxidizing/reducing role
- Dilute HNO3 acts as an oxidizing agent. Nitrate (NO3–) oxidizes iron (Fe → Fe3+) and itself is reduced (typically to NO under these conditions).
Half‑reactions (brief)
- Oxidation: Fe → Fe3+ + 3 e–
- Reduction: NO3– + 4 H+ + 3 e– → NO + 2 H2O
Overall balanced equation
Fe + 4 HNO3 → Fe(NO3)3 + NO + 2 H2O
This shows iron is oxidized to Fe3+ (yellow/brown solution) while nitrate is reduced to NO (sometimes observed as brown NO2 after oxidation in air).
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