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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Electrochemistry describes electron transfer through oxidation and reduction, identifies oxidizing and reducing agents, and applies oxidation numbers to balance redox equations. It also covers electrode potential and the standard hydrogen electrode, which provides the reference for comparing the reduction tendencies of other electrodes.
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