Application of thermodynamics at different scales to describe the behaviour of fast reacting binary mixtures in vapour-liquid equilibrium

•The thermodynamics of fluids in phase and reaction equilibrium is investigated.•A multi-scale methodology is proposed to model reactive fluids thermodynamics.•The proposed methodology is validated on the reactive system N2O4(g/l) = 2 NO2(g/l)•Quantum Mechanics and Monte Carlo simulations are performed.•A predictive accurate equation of state is proposed and its accuracy assessed.