Statistical thermodynamic description of H2 molecules in normal ortho/para mixture

In this paper, an expression for the internal partition function of normal hydrogen has been obtained starting from the principles of classical statistical thermodynamics. The calculated contribution applies to ideal gas properties. Particular attention has been devoted to the entropy, which depends on the logarithm of the partition function. Comparison between normal and equilibrium hydrogen together with theoretical and experimental data available in literature has been discussed. Tables of the thermodynamic properties of hydrogen and hydrogen ion are also reported.