Fundamental restrictions of the second-law and Arrhenius plot methods used in the determination of reaction enthalpies in decomposition kinetics

The apparent increase of the reaction enthalpy Delta H with temperature due to the self-cooling and condensation effects is responsible for the fundamental restrictions of the second-law and Arrhenius plot methods related to determination of this parameter. Theoretical analysis and a comparison with the experimental data indicate that the systematic underestimation of Delta H magnitudes determined by the second-law method equals 10-25% for the reactants decomposed to gaseous products and 15-50% for reactants decomposed to solids. Therefore, the use of these methods in decomposition kinetics is hardly acceptable. The replacement of the Arrhenius plot and second-law methods to the much more precise and accurate third-law method is desirable or even obligatory.