Which of the following substance is a gas at room temperature and atmospheric pressure

Options

A. Iodine
B. Benzene
C. Chloroform
D. Methane

Answer

To determine which substance is a gas at room temperature and atmospheric pressure, we will analyze the boiling points of the given substances: Iodine (I2), Benzene (C6H6), Chloroform (CHCl3), and Methane (CH4).

### Step-by-Step Solution:

1. **Identify the substances**: The substances we need to analyze are:
- Iodine (I2)
- Benzene (C6H6)
- Chloroform (CHCl3)
- Methane (CH4)

2. **Check the boiling point of Iodine (I2)**:
- Iodine has a boiling point of 184.4°C.
- Since 184.4°C is much higher than room temperature (approximately 20°C), Iodine is not a gas at room temperature.

3. **Check the boiling point of Benzene (C6H6)**:
- Benzene has a boiling point of 80.1°C.
- This is also significantly higher than room temperature, so Benzene is not a gas at room temperature.

4. **Check the boiling point of Chloroform (CHCl3)**:
- Chloroform has a boiling point of 61.2°C.
- Again, this boiling point is higher than room temperature, indicating that Chloroform is not a gas at room temperature.

5. **Check the boiling point of Methane (CH4)**:
- Methane has a boiling point of -161.6°C.
- Since -161.6°C is much lower than room temperature, Methane exists as a gas at room temperature.

6. **Conclusion**:
- Among the substances analyzed, only Methane (CH4) has a boiling point lower than room temperature, making it the only gas at room temperature and atmospheric pressure.

### Final Answer:
The substance that is a gas at room temperature and atmospheric pressure is **Methane (CH4)**.

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