Entropy generation rate in a chemically reacting system

For a nonchemical-equilibrium state of an isolated system A that has r constituents with initial amounts na and that is subject to τ chemical reaction mechanisms, temperature, pressure, and chemical potentials cannot be defined. As time evolves, the values of the amounts of constituents vary according to stoichiometric relations. For such a state, we approximate the values of all the properties at time t with the corresponding properties of the stable equilibrium state of a surrogate system B consisting of the same constituents as A with amounts equal to Ni(t) but experiencing no chemical reactions. It is noteworthy that, for the first time, the Onsager relations are proven without reference to microscopic reversibility. In our view, if a process is irreversible, microscopic reversibility does not exist.