CaCO3aq Ion Pair
A user is asking how the existence of CaCO3(aq) was identified. Was it physically measured and identified or just assumed for modeling convenience?
The properties of CaCO3(aq) were determined by regressing a very large body of experimental data (primarily solubilities in Ca – Na – K - Mg – CO3 – Cl systems). No spectroscopic data were available for the concentration of the CaCO3(aq) ion pair (we typically use such data whenever they are available). Therefore, the properties of the ion pair were regressed as adjustable parameters, but they are constrained by a very large data set of solubility data.