Question

The variation of the boiling points of the hydrogen halides is in the order $HF>HI>HBr>HCl$. What explains the higher boiling point of hydrogen fluoride?

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• A. There is strong hydrogen bonding between $HF$ molecules.
• B. The electronegativity of fluorine is much higher than for other elements in the group.
• C. The bond energy of $HF$ molecules is greater than in other hydrogen halides.
• D. The effect of nuclear shielding is much reduced in fluorine which polarises the $HF$ molecule.

Answer 1

The correct option is A There is strong hydrogen bonding between $HF$ molecules.

First option is related to the bond energy. The bond energy is required to break the bond. In the hydrogen halides, $HF$ requires a large amount of energy due to the presence of strong hydrogen bonding.
Now, the nuclear shielding, and the electronegativity, in $HF$ there is the attraction of electrons, so it shows the high electronegativity, and it is a very polar molecule.
So, the boiling point of $HF$ molecule is higher due to the presence of strong hydrogen bonding between $HF$ molecules.
Hence, the correct option is (d).