Chemical reaction equilibrium thermochemical data calculations

The reader should refer to the original tables for the reference material on which the thermochemical data are based. The reference state used in Chapter 1 was chosen as 298 K consequently, the thermochemical values at this temperature are identified from this listing. The logarithm of the equilibrium constant is to the base 10. The unit notation (J/K/mol) is equivalent to (JK mol ). Supplemental thermochemical data for species included in the reaction listing of Appendix C, and not given in Table A2, are listed in Table A3. These data, in combination with those of Table A2, may be used to calculate heats of reaction and reverse reaction rate constants as described in Chapter 2. References for the thermochemical data cited in Table A3 may be found in the respective references for the chemical mechanisms of Appendix C. 

In the 1920s the developing chemical technology required reliable physicochemical data. The accuracy of the thermochemical data available was hardly adequate for the calculations of enthalpies of chemical reactions and completely insufficient for the calculation of equilibrium constants. If reliable values of equilibrium constants were to be calculated, the accuracy of the thermochemical data would have to be increased by about one order of magnitude. The classical period of thermochemistry may be considered to have ended with this understanding. 

Knowledge of the thermodynamics of HDT reactions is necessary for predicting chemical equilibrium. Detailed thermochemical data on individual reactions of complex feedstocks are generally unavailable [24]. The literature offers some generalizations about each type of reaction made from theoretical calculations and few experimental studies with model compounds. For modeling proposes, the equilibrium constants are usually approximated using group contribution methods. 

IVTANTHERMO consists of several databases and a set of algorithms and programs. The databases contain auxiliary data, for example, fundamental physical constants, atomic masses of elements etc. -, constants necessary for the calculations of thermodynamic functions primary experimental data on equilibrium constants of chemical reactions and on saturated vapor pressure of substances thermochemical constants tabulated values of thermodynamic properties for wide temperature intervals. 

Each equilibrium constant can be found by using appropriate thermochemical data, as discussed in Section 9.4. Once values for Ki and are obtained. Equations (E9.18C) and (E9.18D) can be solved for unknowns and 2- Notice that the specific values given by will differ from that given by Equation (E9.16D) hence the value of 2 will also be different. However, the compositions that are calculated will turn out identical to those in Example 9.16. This result illustrates the magic of chemical reaction equilibria No matter what set of independent reactions we pick, the equilibrium compositions that are calculated remain the same. 

Because of the lack of high-pressure experimental reaction rate data for HMX and other explosives with which to compare, we produce in Figure 15 a comparison of dominant species formation for decomposing HMX that have been obtained from entirely different theoretical approaches. The concentration of species at chemical equilibrium can be estimated through thermodynamic calculations with the Cheetah thermochemical code.32,109... 

---