Why does hydrochloric acid have a higher boiling point than diatomic fluorine?

1 Answer
anor277
Aug 11, 2017

Well, consider the intermolecular forces that operate within each substance......

Explanation:

Hydrogen chloride, is a room temperature gas. Its normal boiling point is #-85# #""^@C#. Fluorine is a diatomic molecule, whose normal boiling point is #-188# #""^@C#. Note that #HCl# is water soluble to the tune of #10-11*mol*L^-1#, and in this solution ionization occurs to give hydrochloric acid:

#HCl(g) stackrel(H_2O)rarrH_3O^+ + Cl^-#

Why the disparity in boiling point? Well hydrogen chloride is a larger, more diffuse, molecule, that has more opportunity for a dispersion forces. However, the principle intermolecular force that operates between hydrogen chloride molecules is hydrogen bonding; i.e. #""^(delta+)H-Cl^(delta-)#. The dipoles line up in the bulk phase, and this constitutes a potent intermolecular force......hence the respective boiling points.

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