This is an updated perspective of the subject based on the concepts that the thermodynamic properties of a system are independent whether composition is specified in terms of formal components or molecular species and that the laws of thermodynamics are independent of the observational time-scale. By applying these concepts, the author has derived approximately 20 general theorems concerned with the thermodynamic properties of molecular species to include all participants in reaction mechanisms. Proved theories are supplemented with verbal explanations and explicit examples. Applications...