Which oxides of Nitrogen are generated by burning of fossil fuel ?

Question

Accepted Answer

Option 1, which states that the oxides of nitrogen generated by the burning of fossil fuels are NO and $NO_2$, is correct. Here's a detailed explanation:

1. **Explanation for Option 1 (Correct Answer):**
   - **Nitric Oxide (NO):** When fossil fuels are burned at high temperatures, nitrogen and oxygen from the air react to form nitric oxide (NO). This is a primary pollutant directly emitted from combustion processes.
   - **Nitrogen Dioxide ($NO_2$):** Nitric oxide can further react with oxygen in the atmosphere to form nitrogen dioxide ($NO_2$). This is a secondary pollutant and is a significant component of smog and air pollution.
   - Both NO and $NO_2$ are collectively referred to as NOx, which is a common term for nitrogen oxides produced from combustion, especially in vehicles and industrial processes.

2. **Explanation for why other options are incorrect:**

- **Option 2 ($NO_2, NO_3$ and $N_2O_5$):**
     - While $NO_2$ is indeed produced from fossil fuel combustion, $NO_3$ (nitrate radical) and $N_2O_5$ (dinitrogen pentoxide) are not directly emitted from combustion. $NO_3$ is typically formed in the atmosphere through complex reactions involving $NO_2$ and other radicals, and $N_2O_5$ is formed under specific atmospheric conditions, usually at night, from the reaction of $NO_2$ and $NO_3$.

- **Option 3 ($N_2O_3$ and $N_2O_5$):**
     - $N_2O_3$ (dinitrogen trioxide) and $N_2O_5$ are not primary products of fossil fuel combustion. These compounds are formed under specific atmospheric conditions and are not directly emitted from combustion processes.

- **Option 4 ($NO_3$ and $N_2O_5$):**
     - As mentioned earlier, $NO_3$ and $N_2O_5$ are not directly produced from the burning of fossil fuels. They are formed through secondary reactions in the atmosphere and are not considered primary pollutants from combustion.

In conclusion, Option 1 is the correct answer because NO and $NO_2$ are the primary nitrogen oxides generated directly from the combustion of fossil fuels. The other options include compounds that are not directly emitted from such processes.