Enthalpy calculation with Born-Haber cycle

The standard gas phase acidity of HN3 has an enthalpy of 1439 8kJ/mol and was measured by ion cyclotron resonance of gas-phase proton transfer reactions. This result disagrees with values calculated from Born-Haber cycles [1]. Thermodynamic data for the dissociation in aqueous solution are given on p. 151. 

The lattice enthalpy U at 298.20 K is obtainable by use of the Born—Haber cycle or from theoretical calculations, and q is generally known from experiment. Data used for the derivation of the heat of hydration of pairs of alkali and halide ions using the Born—Haber procedure to obtain lattice enthalpies are shown in Table 3. The various thermochemical values at 298.2° K [standard heat of formation of the crystalline alkali halides AHf°, heat of atomization of halogens D, heat of atomization of alkali metals L, enthalpies of solution (infinite dilution) of the crystalline alkali halides q] were taken from the compilations of Rossini et al. (28) and of Pitzer and Brewer (29), with the exception of values of AHf° for LiF and NaF and q for LiF (31, 32, 33). The ionization potentials of the alkali metal atoms I were taken from Moore (34) and the electron affinities of the halogen atoms E are the results of Berry and Reimann (35)4. 

The enthalpy of formation of an ionic compound can be calculated with an accuracy of a few percent by means of the Born-Land equation (Eq. 4.13) and the Born-Haber cycle. Consider NaCI. for example. Wc have seen that by using the predicted internuclear distance of 283 pm (or the experimental value of 281.4 pm), the Madelung constant of 1.748, the Born exponent, n, and various constants, a value of —755kJmor could be calculated for the lattice energy. The heat capacity correction is 2.1 kJ mol", which yields = —757 kJ moP. The Bom-Haber summation is then... 

FIGURE 28 Crystalline radii for the ions O), calculated using the Born-Haber cycle and Kapustinskii s equation from the enthalpies of formation found with the use of Kim and Oishi s scheme (Kim and Oishi, 1979) A, Shannon s data (Shannon, 1976). The solid curve connects the values calculated from the fit of polynomial (28). Reproduced from Chervonnyi and Chervonnaya (2005c) with permission from Pleiades Publishing, Ltd. 

Based on the above calculations, both the free energy function (EEE) and the standard enthalpy of formation AH° (298) of NiCp were obtained, the first from its structure and normal mode of vibration by applying the harmonic-oscillator, rigid-rotator approximation, and the second from a Born-Haber thermodynamic cycle.The thermodynamic description of NiCp, together with that of the other participating compounds, permitted a second series of partial equilibrium calculations of the... 

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