Which of the following compound has a least heating value?

Options

A. Alcohol
B. Biogas
C. Wood
D. Coal

Answer

To determine which compound has the least heating value among the given options (alcohol, biogas, wood, and coal), we need to understand the concept of heating value.

### Step-by-Step Solution:

1. **Understanding Heating Value**:
- Heating value (or calorific value) is the amount of energy released when a substance is completely burned. It is usually expressed in kilojoules per gram (kJ/g) or megajoules per kilogram (MJ/kg).

2. **Comparing the Options**:
- **Alcohol**: Generally has a high heating value because it is a hydrocarbon and burns efficiently.
- **Biogas**: Contains methane and has a moderate heating value, typically higher than wood but lower than coal.
- **Wood**: Has a lower heating value compared to fossil fuels. The heating value can vary depending on the type of wood but is generally lower than that of coal and alcohol.
- **Coal**: Typically has a high heating value as it is a fossil fuel with a high carbon content.

3. **Identifying the Compound with the Least Heating Value**:
- Among the four options, wood is known to have the least heating value. This is due to its composition and the presence of moisture content which reduces its efficiency in energy release.

4. **Conclusion**:
- Therefore, the compound with the least heating value is **wood** (Option 3).

### Final Answer:
The compound with the least heating value is **wood** (Option 3).

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