A redox reaction is shown below:C° + 4HNO3 (conc.) ⟶CO2 + 4NO2 + 2H2OIn this reaction oxidation number of N from nitric acid to NO2 is decreased from _to_.
Correct answer: B. +5 to +4
- A. +5 to +2
- B. +5 to +4
- C. +3 to +2
- D. +4 to +2
Explanation
In the given redox reaction, the nitrogen in nitric acid (HNO3) has an oxidation number of +5. During the reaction, it is reduced to nitrogen dioxide (NO2) where the oxidation number is +4. This change from +5 to +4 indicates a reduction because the nitrogen atom gains electrons. The correct answer is therefore +5 to +4. Other options are incorrect because they either do not start at the correct oxidation number for nitrogen in HNO3 or do not reflect the actual decrease in oxidation number.
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