Brown vapours can be of

Options

A. `Cl_(2)`
B. `l_(2)`
C. `Br_(2)`
D. `NO_(2)`

Answer

To determine which substances can produce brown vapors, we will analyze each option provided in the question: Cl2, I2, Br2, and NO2.

### Step-by-Step Solution:

1. **Analyze Cl2 (Chlorine gas)**:
- Chlorine gas is known to have a greenish-yellow color.
- **Conclusion**: Cl2 does not produce brown vapors.
- **Result**: Incorrect option.

2. **Analyze I2 (Iodine)**:
- Iodine vapor is characterized by a deep purple color.
- **Conclusion**: I2 does not produce brown vapors.
- **Result**: Incorrect option.

3. **Analyze Br2 (Bromine)**:
- Bromine is known for its reddish-brown color.
- **Conclusion**: Br2 can produce brown vapors.
- **Result**: Correct option.

4. **Analyze NO2 (Nitrogen dioxide)**:
- Nitrogen dioxide is also reddish-brown in color.
- **Conclusion**: NO2 can produce brown vapors.
- **Result**: Correct option.

### Final Answer:
The substances that can produce brown vapors are **Br2 (Bromine)** and **NO2 (Nitrogen dioxide)**. The options Cl2 and I2 do not produce brown vapors.

### Summary of Results:
- Cl2: Incorrect (greenish-yellow)
- I2: Incorrect (deep purple)
- Br2: Correct (reddish-brown)
- NO2: Correct (reddish-brown)