In the series HCl, HBr and HI, the boiling point increases in the order `HC l lt HB r lt HI`. Thiis is due to:

Options

A. HI is the strongest acid among the series
B. HI is the strongest reducing agent among the series
C. higherr van der waals' forces of attraction in HI
D. intermolecular H-bonding in HI

Answer

To solve the question regarding the boiling points of HCl, HBr, and HI, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Compounds**: We are looking at three hydrogen halides: HCl (hydrochloric acid), HBr (hydrobromic acid), and HI (hydroiodic acid).

2. **Understand Boiling Points**: The boiling point of a substance is influenced by the strength of intermolecular forces present. In the case of hydrogen halides, the primary intermolecular forces at play are Van der Waals forces (dispersion forces) and dipole-dipole interactions.

3. **Consider Atomic Mass**: As we move down the group in the periodic table from chlorine to bromine to iodine, the atomic mass of the halogens increases.
- HCl has Cl (atomic mass ~35.5 g/mol)
- HBr has Br (atomic mass ~80 g/mol)
- HI has I (atomic mass ~127 g/mol)

4. **Relate Atomic Mass to Van der Waals Forces**: Larger atoms have more electrons, which leads to stronger Van der Waals forces due to increased polarizability. Therefore, as the atomic mass increases, the strength of the Van der Waals forces also increases.

5. **Order of Boiling Points**: Since HI has the largest atomic mass, it will have the strongest Van der Waals forces, followed by HBr, and then HCl with the weakest. This results in the following order of boiling points:
- HI > HBr > HCl

6. **Conclusion**: The increase in boiling points from HCl to HBr to HI is primarily due to the increasing strength of Van der Waals forces as the atomic mass of the halogen increases.

### Final Answer:
The boiling point increases in the order HCl < HBr < HI due to the high Van der Waals forces of attraction in HI compared to HBr and HCl.

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