[en] Highlights: • Hydrogen dissociation reaction was studied via computer simulation. • Reactive force field ReaxFF provide comparable quality with the three body potential. • Thermodynamic properties of reaction are specified. • We report the heat of reaction (302 kJ/mol) and activation energy barrier (438 kJ/mol). We present thermodynamic properties of the H₂ dissociation reaction by means of the Small System Method (SSM) using Reactive Force Field (ReaxFF) simulations. Thermodynamic correction factors, partial molar enthalpies and heat capacities of the reactant and product were obtained in the high temperature range; up to 30,000 K. The results obtained from the ReaxFF potential agree well with previous results obtained with a three body potential (TBP). This indicates that the popular reactive force field method can be combined well with the newly developed SSM in realistic simulations of chemical reactions. The approach may be useful in the study of heat and mass transport in combination with chemical reactions.