Which of the following is redox reaction ?

Options

A. `H_(2)SO_(4)` reach with NaOH
B. In atmoshere, `O_(3)` is formed from `O_(2)` by lightning
C. Evaporation of `H_(2)O`
D. Oxides of nitrogen are formed form nitrogen & oxygen by lightning

Answer

To determine which of the given reactions is a redox reaction, we will analyze each option based on the definition of redox reactions, which involve the transfer of electrons between species, leading to changes in their oxidation states.

### Step-by-Step Solution:

1. **Identify the Reactions**:
- We have four reactions to analyze:
- A: H2SO4 + NaOH
- B: O2 → O3 (by lightning)
- C: Evaporation of water
- D: N2 + O2 → Nitrogen oxides (by lightning)

2. **Analyze Option A: H2SO4 + NaOH**:
- This is an acid-base neutralization reaction.
- H2SO4 (sulfuric acid) donates protons (H+) to NaOH (sodium hydroxide), forming Na2SO4 (sodium sulfate) and water (H2O).
- There is no change in oxidation states of the elements involved.
- **Conclusion**: Not a redox reaction.

3. **Analyze Option B: O2 → O3**:
- This reaction involves the formation of ozone (O3) from oxygen (O2).
- The oxidation state of oxygen remains the same (0 in O2 and 0 in O3).
- No electron transfer occurs.
- **Conclusion**: Not a redox reaction.

4. **Analyze Option C: Evaporation of Water**:
- In this process, water (H2O) changes from liquid to vapor.
- There is no change in oxidation states; water remains H2O in both states.
- **Conclusion**: Not a redox reaction.

5. **Analyze Option D: N2 + O2 → Nitrogen Oxides**:
- In this reaction, nitrogen (N2) and oxygen (O2) react to form nitrogen oxides (e.g., NO, NO2).
- The oxidation state of nitrogen changes from 0 in N2 to +2 in NO (or +4 in NO2).
- The oxidation state of oxygen changes from 0 in O2 to -2 in the nitrogen oxides.
- This indicates that nitrogen is oxidized and oxygen is reduced.
- **Conclusion**: This is a redox reaction.

6. **Final Answer**:
- The only redox reaction among the options is **Option D: N2 + O2 → Nitrogen Oxides**.