Least volatile hydrogen halide is

Options

A. HF
B. HCl
C. HBr
D. Hl

Answer

To determine the least volatile hydrogen halide among HF, HCl, HBr, and HI, we can follow these steps:

### Step 1: Understand Volatility
Volatility refers to how readily a substance vaporizes. Substances with strong intermolecular forces tend to be less volatile because more energy is required to overcome these forces.

### Step 2: Identify the Hydrogen Halides
The given hydrogen halides are:
- HF (Hydrogen Fluoride)
- HCl (Hydrogen Chloride)
- HBr (Hydrogen Bromide)
- HI (Hydrogen Iodide)

### Step 3: Analyze Intermolecular Forces
1. **HF (Hydrogen Fluoride)**: HF exhibits strong hydrogen bonding due to the high electronegativity of fluorine. This results in significant intermolecular attraction.
2. **HCl (Hydrogen Chloride)**: HCl has dipole-dipole interactions but does not exhibit hydrogen bonding like HF.
3. **HBr (Hydrogen Bromide)**: Similar to HCl, HBr has dipole-dipole interactions but is even weaker than HCl.
4. **HI (Hydrogen Iodide)**: HI also has dipole-dipole interactions, but it is the weakest among the hydrogen halides due to the larger size of iodine.

### Step 4: Compare the Intermolecular Forces
- HF has strong hydrogen bonding, making it less volatile.
- HCl, HBr, and HI have weaker dipole-dipole interactions, making them more volatile compared to HF.

### Step 5: Conclusion
Since HF has strong hydrogen bonding, it is the least volatile among the hydrogen halides listed. Therefore, the answer is **HF**.

### Final Answer
The least volatile hydrogen halide is **HF**.

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