The accurate prediction of thermodynamic properties of systems in thermodynamic equilibrium is crucial for the design of efficient processes in the chemical industry. The model employed in this thesis is the heterosegmental Perturbed Chain Statistical Associating Fluid Theory equation of state (PC-SAFT). PC-SAFT is a widely used thermodynamic model, which is especially suited to describe the behavior of complex fluids and associating substances. The heterosegmental approach of PC-SAFT allows for separation of molecules into various segments which are each characterized by a set of model parameters. The model was utilized to predict the behavior of butane - alcohol systems, revealing that the two-phase region widens with an increasing number of C-atoms on the alcohol and narrows with higher temperatures. Furthermore, the mixture approaches the behavior of an ideal solution as the number of carbon atoms increases. When modeling butanol - alkane systems, it was observed that the two-phase region narrows with increasing temperature, but no widening trend was observed with an increase in the number of carbon atoms in the alkane. The application of the model to predict the behavior of binary n-alcohol - carbon dioxide (CO2) systems revealed limited accuracy in modeling the complete miscibility gap. Although the results show no significant improvement over the results obtained with the homosegmental approach, the heterosegmental approach offers the advantage of a single temperature-dependent binary parameter for all CO2 - alcohol systems, whereas the homosegmental approach requires fitting multiple parameters for each unique system. While neither approach precisely predicts the vapor-liquid equilibria across the entire temperature and pressure range, the heterosegmental approach yields comparable or superior outcomes with the convenience of fitting a single binary parameter. Additionally, it was demonstrated that the modeling results for ethane - butanol and propane - butanol systems also exhibit deviations near the critical region, akin to those observed in CO2 - alcohol systems.