Abstract: Based on the analysis of the molecular association (dimerization) phenomenon of some polar gases, the equations for calculating the equilibrium constants and heats of dimerization for polar gases are proposed. In addition, the equation for calculating the second virial coefficient of the simply truncated virial equation of state for describnig FVT behavior of gases at low pressure is also modified by introducing the equilibrium constant. The proposed equations were tested, and satisfactory results are obtained.

Key words: Molecular aggregation, Equilibrium constant of association, Enthalpy of association, Viri-al equation