Which of the following reactions is an exothermic reaction?

Options

A. Burning of coal.
B. Decomposition of vegetable matter into compost.
C. Process of respiration.
D. Decomposition of calcium carbonate to form quicklime and carbon dioxide.

Answer

To determine which of the following reactions is an exothermic reaction, we need to understand what an exothermic reaction is. An exothermic reaction is a chemical reaction that releases heat to its surroundings.

Let's analyze each option provided:

1. **Burning of coal**: This is a combustion reaction where coal reacts with oxygen to produce carbon dioxide, water, and heat. Since heat is released during this reaction, it is an exothermic reaction.

2. **Decomposition of vegetable matter into compost**: This process involves the breakdown of organic matter by microorganisms, which also releases heat as a byproduct. Therefore, this reaction is also exothermic.

3. **Process of respiration**: In cellular respiration, glucose reacts with oxygen to produce carbon dioxide, water, and energy (in the form of heat). This process releases heat, making it an exothermic reaction.

4. **Decomposition of calcium carbonate to form quicklime and carbon dioxide**: This reaction is an endothermic reaction, as it requires heat to break down calcium carbonate into calcium oxide (quicklime) and carbon dioxide. Therefore, this reaction does not release heat.

Based on the analysis:
- The reactions that are exothermic are:
- Burning of coal (Option 1)
- Decomposition of vegetable matter into compost (Option 2)
- Process of respiration (Option 3)

Thus, the correct answer is that options 1, 2, and 3 are exothermic reactions.

### Final Answer:
The exothermic reactions are:
- Burning of coal (Option 1)
- Decomposition of vegetable matter into compost (Option 2)
- Process of respiration (Option 3)