Standard States
The standard states used here are listed in the following. They are in accordance with IUPAC recommendations.[1]
T = 298.15 K
p = 105 Pa
All values are given in the mol L−1 scale.
Gibbs solvation energies are given as the transfer of particles from p = 105 Pa in the gaseous state to c = 1 mol L−1 in the solvation state.
We use the EC-B convention according to Bartmess.[2]
We use as main anchor point the value for the hydration of the proton as determined by Tissandier et al.:[3]
ΔsolvG°(H+, H2O) = −1104.5 kJ mol−1.
However, the value recommended by Hünenberger et al. is quite similar:[4]
ΔsolvG°(H+, H2O) = −1100.0 kJ mol−1.
Note that this value is given in the EC-FD convention and in the mol kg−1 scale. For the proton, the EC-B value is shifted by about −3.6 kJ mol−1 with respect to the EC-FD value (for other ions the shift is negligible). For hydration, the distinction between the mol L−1 and the mol kg−1 scale is considered to be negligible (ca. 0.007 kJ mol−1). Changing the mol L−1 scale into the mol kg−1 scale, the pHabs value changes by 1 pH unit for the tenfold increase or decrease of the solvents density compared to 1 kg L−1. Most solvents lie in the range of 0.75 – 1.25 kg L−1, thus the changes lie in the range of about −0.1 to +0.1 pH units depending on the solvent.
For values taken from the literature, we cannot know with certainty those states that are not specified exactly. In such cases, we have attempted to deduce the standard states from the context. It should be noted, however, that values published before 1994 cannot of course be given in the EC-FD convention. To the best of our knowledge and belief, the ΔsolvG°- and ΔtrG°-values listed on this website all refer to the same standard states.
The detailed description can be found under
V. Radtke et al., Pure Appl. Chem. 2021, 93(9), 1049.
[1] M. B. Ewing, T. H. Lilley, G. M. Olofsson, M. T. Ratzsch, G. Somsen, Pure Appl. Chem. 1994, 66, 533.
[2] J. E. Bartmess, J. Phys. Chem. 1994, 98, 6420.
[3] M. D. Tissandier, K. A. Cowen, W. Y. Feng, E. Gundlach, M. H. Cohen, A. D. Earhart, J. V. Coe. J. Phys. Chem. A 1998, 102, 7787–7794.
[4] P. Hünenberger, M. Reif, Single-Ion Solvation. Experimental and Theoretical Approaches to Elusive Thermodynamic Quantities, The Royal Society of Chemistry, Cambridge, 2011.