Bond dissociation energy hydrogen halides

The heats of formation of the gaseous atoms, 4, are not very different clearly, it is the change in the bond dissociation energy of HX, which falls steadily from HF to HI, which is mainly res ponsible for the changes in the heats of formation. 6. We shall see later that it is the very high H—F bond energy and thus the less easy dissoeiation of H—F into ions in water which makes HF in water a weak aeid in comparison to other hydrogen halides. 

FIGURE 2.18 The bond dissociation energies of the hydrogen halide molecules in kilojoules per mole of molecules. Note how the bonds weaken as the halogen atom becomes larger. 

Fig. 17.12 Bond dissociation energies and bond lengths of the hydrogen halides, methyl halides, and halogen molecules. Note that this figure, which is taken directly from Politzcr s work, portrays in a different way relationships that are closely rebled to Fig. 9.7. (From Politzer. P. J. Am. Chetn. See. 1969. 91.6235. Reproduced with permission.)...

TABLE 15.6 Bond Dissociation Energies for Hydrogen Halides and Acid Strengths for Hydrohalic Acids... 

Table 18.1. Gaseous hydrogen halides, methyl halides or dihalogens XCl X-H, X-C and X-Cl bond distances (in pm) and bond dissociation energies (in kJ mol ).

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