  All current formulations of nonequilibrium thermodynamics of open chemical
reaction networks rely on the assumption of non-interacting species. We develop
a general theory which accounts for interactions between chemical species
within a mean-field approach using activity coefficients. Thermodynamic
consistency requires that rate equations do not obey to standard mass-action
kinetics, but account for the interactions with concentration dependent kinetic
constants. Many features of the ideal formulations are recovered. Crucially,
the thermodynamic potential and the forces driving non-ideal chemical systems
out of equilibrium are identified. Our theory is general and holds for any
mean-field expression of the interactions leading to lower bounded free
energies.
