Table 1. Thermodynamic and Structural Properties of Different Complexes of Ca2+ with Hydrogen Phosphate Anions in Watera.
| species | number of OW in coordination shell | change in OW in coordination shell | ΔGassn (kJ/mol) | ΔGfrom ions (kJ/mol) |
|---|---|---|---|---|
| Ca2+ | 7.2245 | |||
| [CaHPO4]0 | 5.06 | –2.16 | –17.9 | –17.9 |
| [Ca(HPO4)2]2– | 4.05 | –1.01 | –12.0 | –29.9 |
| [Ca(HPO4)3]4– | 3.05 | –1.00 | +1.1 | –28.7 |
a
The average number of water oxygens (OW) in the hydration shell of the calcium cation, either as an isolated ion in water or within an ion pair or complex, is given in the second column. The change in water coordination number and free energy of one association (ΔGassn) are given relative to the species on the previous line of the table in the third and fourth columns, respectively. The free energy of the species formed from ions is reported in the fifth column.