Which among the following will boil at highest temperature?

Options

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

Answer

To determine which compound among HF, HCl, HBr, and HI will boil at the highest temperature, we need to analyze the intermolecular forces present in each compound.

### Step-by-Step Solution:

1. **Understanding Boiling Point**: The boiling point of a substance is influenced by the strength of the intermolecular forces present. Stronger intermolecular forces lead to higher boiling points.

2. **Identifying the Compounds**: The compounds in question are:
- HF (Hydrogen Fluoride)
- HCl (Hydrogen Chloride)
- HBr (Hydrogen Bromide)
- HI (Hydrogen Iodide)

3. **Analyzing Intermolecular Forces**:
- **HF**: Exhibits hydrogen bonding due to the presence of highly electronegative fluorine. This results in strong intermolecular forces.
- **HCl**: Has dipole-dipole interactions but does not exhibit hydrogen bonding. The intermolecular forces are weaker than those in HF.
- **HBr**: Similar to HCl, it has dipole-dipole interactions, but the molecular weight is higher, leading to slightly stronger Van der Waals forces compared to HCl.
- **HI**: Also has dipole-dipole interactions, but with an even higher molecular weight, resulting in stronger Van der Waals forces compared to HBr.

4. **Comparing the Strength of Intermolecular Forces**:
- HF has the strongest intermolecular forces due to hydrogen bonding.
- HI has the highest molecular weight, which contributes to stronger Van der Waals forces, but lacks hydrogen bonding.
- HBr has stronger forces than HCl but weaker than HF.
- HCl has the weakest intermolecular forces among the four.

5. **Conclusion**: Since HF has hydrogen bonding, which is a stronger intermolecular force compared to the dipole-dipole interactions present in HCl, HBr, and HI, HF will have the highest boiling point.

### Final Answer:
**HF (Hydrogen Fluoride) will boil at the highest temperature among the given options.**