Appearance energy thermochemical cycle

Figure 4.3 Thermochemical cycle, showing how the experimental appearance energy of A+(A exp) is related to the appearance energies at 0 K and temperature T. AH(1), AH(2), and T are defined in the text. Adapted from [64].

Like that of the hydrated electron and the hydrogen atom, the potential of the hydroxyl radical has long been the subject of estimates based on thermochemical cycles involving the free energy of hydration of OH the results of these calculations appear, for example, in Standard Potentials (pp. 59-64). Recently, however, there have been two direct determinations of E° for the OH/OH- couple. In the first, Schwarz and Dodson (279) used pulse radiolysis to measure the equilibrium constants for... 

The bond dissociation energies D(F2N-F), D(FN-F), and D(N-F) have been obtained from appearance potentials (AP) of fragment ions in mass spectra combined with ionization potentials (IP) of the neutral precursors, thermochemical values for atomization enthalpies (AHgt), and standard enthalpies of formation (AH°) of NF3 and NFg [1 to 3]. They have also been obtained from thermochemical cycles alone [4,5]. D(F2N-F) was also directly determined from the equilibrium constant of the gas-phase reaction NF3 Np2+ F [6]. The values are compiled in Table 4. 

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