Which is the same thing as saying that HCl, and HBr, and HI, have LOWER boiling points than that of HF.
AS a chemist, as a physical scientist, it is your responsibility to assess data not remember them, and we list the NORMAL boiling points as follows:
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WHY are the boiling points of HF and H2O so disproportionately high? The answer is intermolecular hydrogen bonding. That is the electronegative fluorine atom polarizes electron density towards itself to give a resultant molecular dipole, i.e. a separation of charge: −δF−Hδ+.
In the condensed phase, these dipoles line up to give a strong contributor to intermolecular force: −δF−Hδ+⋅F−H⋅F−H etc.
And thus HF is the LEAST VOLATILE hydrogen halide.
Note that hydrogen bonding also occurs for HCl, and HI, and also H2S, but because the dipole is of smaller magnitude, hydrogen-bonding does not make such a contribution to intermolecular force. The boiling points here follow the order of dispersion force, which increase with the number of electrons, and thus with the atomic number of the halogen/chalcogen.
