Which of the following hydrogen halide is liquid at 273K?

Options

A. HI
B. HBr
C. HCI
D. HF

Answer

To determine which hydrogen halide is liquid at 273 K, we will analyze the properties of each hydrogen halide mentioned in the question.

### Step-by-step Solution:

1. **Identify the Hydrogen Halides**: The hydrogen halides in question are:
- Hydrogen Iodide (HI)
- Hydrogen Bromide (HBr)
- Hydrogen Chloride (HCl)
- Hydrogen Fluoride (HF)

2. **Understand the Physical States at 273 K**: At 273 K (0 °C), we need to consider the physical state (gas, liquid, or solid) of each hydrogen halide.

3. **Analyze Hydrogen Iodide (HI)**:
- HI is a gas at room temperature and remains a gas at 273 K due to weak Van der Waals forces.

4. **Analyze Hydrogen Bromide (HBr)**:
- HBr is also a gas at room temperature and remains a gas at 273 K for similar reasons as HI.

5. **Analyze Hydrogen Chloride (HCl)**:
- HCl is a gas at room temperature and continues to be a gas at 273 K, again due to weak intermolecular forces.

6. **Analyze Hydrogen Fluoride (HF)**:
- HF is unique among these hydrogen halides. It exhibits strong hydrogen bonding due to the high electronegativity of fluorine and the small size of the fluorine atom. This leads to stronger intermolecular forces compared to the other hydrogen halides.

7. **Conclusion**: Due to the extensive hydrogen bonding in HF, it can exist as a liquid at 273 K, while the other hydrogen halides remain gaseous. Therefore, the answer to the question is:
- **Hydrogen Fluoride (HF)** is the only hydrogen halide that is liquid at 273 K.

### Final Answer:
**Hydrogen Fluoride (HF)** is liquid at 273 K.

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