Which of these is an example of incomplete combustion?

Options

A. Red flame from burning charcoal
B. Black smoke of candle
C. Yellow flame of candle
D. Blue flame of burner

Answer

To determine which of the given options is an example of incomplete combustion, we need to understand the characteristics of combustion types:

1. **Complete Combustion**: This occurs when a fuel burns in sufficient oxygen, producing carbon dioxide and water. It typically produces a blue flame.

2. **Incomplete Combustion**: This occurs when there is insufficient oxygen for the fuel to react completely, resulting in the production of carbon monoxide, soot, or other products. It usually produces a yellow or red flame and may also produce smoke.

Now, let's analyze each option:

### Step-by-Step Solution:

1. **Option 1: Red flame from burning charcoal**
- **Analysis**: The red flame indicates that the combustion is not complete due to insufficient oxygen. This is an example of incomplete combustion.
- **Conclusion**: This option is an example of incomplete combustion.

2. **Option 2: Black smoke of candle**
- **Analysis**: Black smoke indicates that there is a lot of unburned carbon, which is a sign of incomplete combustion. However, the description suggests that it is from a dark zone where no combustion occurs, which is misleading.
- **Conclusion**: This option is also indicative of incomplete combustion.

3. **Option 3: Yellow flame of candle**
- **Analysis**: A yellow flame is typically produced when there is insufficient oxygen, leading to incomplete combustion. The yellow color comes from the soot particles that are not fully burned.
- **Conclusion**: This option is an example of incomplete combustion.

4. **Option 4: Blue flame of burner**
- **Analysis**: A blue flame indicates complete combustion, as it shows that the fuel is burning efficiently with sufficient oxygen.
- **Conclusion**: This option is not an example of incomplete combustion.

### Final Answer:
The examples of incomplete combustion are the **red flame from burning charcoal** and the **yellow flame of a candle**. Therefore, the correct answer is the **yellow flame of the candle**.