Equation of state models with a 'chemical' contribution that accounts for association and solvation effects, are computationally intensive as they have to solve an internal chemical equilibrium calculation. Frequently, only the final results of this internal calculation are used in the subsequent evaluation of physical properties from the model. As a consequence, a substantial amount of unneeded work is performed. We show here how the state function minimization in the chemical equilibrium calculation can be utilized to simplify the calculation of physical properties like pressure and chemical potentials and the derivatives of these properties with respect to temperature, volume and composition.