Figure (a) shows a parity plot of the gas phase NH3 molar fraction, 𝑦 , calculated by both the model presented in this study (GEM) and the stoichiometric approach using Shomate equations (SM), which is described in previous work , compared to experimental NH3 molar fractions obtained by Larson and Dodge and Larson for NH3 synthesis (𝜆 = 0). In this limiting case of NH3 synthesis only, the agreement between both calculation methods and the experimentally obtained molar fractions is excellent for pressures up to 100 atm, which is the range relevant in this study. Besides, at 300 atm, the GEM model presented here is still in accordance with the experimental data, while the results obtained from the stoichiometric calculation method deviate more severely. Above 100 atm, the deviations of both models from the experimental results and each other become more pronounced, as shown in the SI and previously observed for the stoichiometric method. One possible reason for the more pronounced differences in the two models at higher pressures is the fact that the GEM model does consider real gas behavior through the incorporation of the activity coefficients, while ideal gas behavior is considered in the SM model as it is used here. However, pressures that high are not relevant for the scope of this study and thus not shown here.