A major source of oxide of nitrogen is from the burning of

1. Analyze the question

The question asks for the primary source of nitrogen oxides ($NO_x$) released into the atmosphere through combustion processes. We need to identify which of the provided options is most associated with the high-temperature combustion that facilitates the reaction between atmospheric nitrogen and oxygen.

2. Explain the concept

Nitrogen oxides (primarily $NO$ and $NO_2$) are formed during combustion processes when nitrogen and oxygen from the air react at very high temperatures. This reaction is represented as:

In the context of environmental chemistry, the burning of fossil fuels in internal combustion engines (like those in cars, trucks, and power plants) is the most significant anthropogenic source of nitrogen oxides. While coal and wood contain some nitrogen, the combustion of liquid petroleum fuel (hydrocarbons) in engines operating at high temperatures and pressures is the classic source taught in the Nigerian secondary school chemistry curriculum regarding air pollution.

3. Show the solution

• Coal (A): While burning coal releases sulfur dioxide ($SO_2$) and carbon dioxide, it is not the primary source of nitrogen oxides compared to internal combustion engines.
• Wood (B): Burning wood releases carbon monoxide and particulate matter, but it is not the major industrial source of $NO_x$.
• Fuel (C): The combustion of fossil fuels (petrol, diesel) in automobile engines is the leading cause of nitrogen oxide emissions. The high temperature of the engine forces the nitrogen in the air to react with oxygen.
• Chlorofluorocarbons (D): These are refrigerants and propellants; they are responsible for ozone layer depletion, not the production of nitrogen oxides.

4. Identify the answer

The correct option is C.

5. Tip

Exam Strategy: When you see questions about "oxides of nitrogen" in the context of pollution, always look for keywords like "automobile exhaust," "internal combustion engines," or "fossil fuels." Remember that $SO_2$ is usually linked to "burning coal/sulfur," while $NO_x$ is linked to "high-temperature combustion of fuels."