摘要
Standard thermodynamic treatments of molecular systems, defined in terms of average properties, require two definitions of equilibrium but cannot explain fully the behaviour of molecular systems where the equilibrium properties are determined by the distribution of molecular energies. They have no explanation for the initiation, propagation and termination of reactions. The treatment proposed here addresses these problems for ideal gas reactions. It shows that the standard explanation, that the kinetic energies of molecular collisions are the sole causes of reactions, is incorrect. It is based on the average properties from the MBD （Maxwell Boltmnann distribution） and its standard deviation, o. It states the principle that explains why two definitions of equilibrium are needed. It provides criteria for the propagation of a reaction, and shows how the mole fraction of reactants needed for propagation, Yi~, can be calculated from the heat capacities of the components. The best heat capacity correlations, due to Harmens, were used to calculate value of Yig.. The energies of the molecules needed to propagate reactions are calculated from the CDF （cumulative distribution function） of the MBD. An alternative method, producing very similar values, is discussed in the following paper. Once the values ofyign are known, the molecular kinetic energies at the ignition temperature can be calculated from the MBD and its CDF. Calculations for four ideal gases show the molecular kinetic energies are much too small, compared to the bond energies, to explain propagation of reactions for four ideal gas mixtures. A proposed explanation, involving excited electronic states also explains why mixtures have ignition temperatures. Correlations for the heat capacities of the reactants which include contributions from electrons in excited states, are needed to establish this.
