Hydronium Hydroxide energies

DOI: 10.14469/hpc/8068 Metadata

Created: 2021-04-04 08:18

Last modified: 2021-04-06 08:55

Author: Henry Rzepa

License: Creative Commons: Public Domain Dedication 1.0

Funding: (none given)


Gaussian 16 calculations. The entropy difference between H3O(+).OH(-).9H2O as a bridged ion pair and separated ions is 188.16 cal/mol/K, or -23.0 in the free energy of separation. This is more or less balanced by the fre energy required to break three strong solvent bridge hydrogen bonds during the separation process. Thus the free energy of the contact ion pair and the solvent-separated ion pairs is approximately the same! The coulomb potential for separating two ions from ~3.3A out to infinity in a water dielectric is small (+1.1 kcal/mol) and does not materially influence this result.

Member of collection / collaboration

10.14469/hpc/177 Computation data for Henry Rzepa's blog


10.14469/hpc/8011 OH.6H2O 6-311++G(d,p/SCRF=water G = -534.557063 Total G = -1,070.004539 DG = -1.2 vs contact ion pair
10.14469/hpc/8017 Hydronium hydroxide, proton transfer to give > 14.H2O G = -1070.041744 DG = -23.3 lower than separated ion pair
10.14469/hpc/8010 OH.3H2O 6-311++G(d,p/SCRF=water E = -305.305881, G = -305.261518. Total for 9H2O = -840.708994
10.14469/hpc/8009 H3O.6H2O 311++G(d,p)/SCRF=water G = -535.447476 Total G = -1,070.004539 DG = -1.2 vs contact ion pair
10.14469/hpc/8021 Hydronium hydroxide. 12H2O G = -1070.002748

Associated DOIs

Current dataset ...DOIDescription
References 10.1002/qua.25703 Challenges in predicting ΔrxnG in solution: Hydronium, hydroxide, and water autoionization
References 10.14469/ch/191994 Hydronium hydroxide, close ion pair with 9H2O bridging
References 10.14469/hpc/8069 Hydronium hydroxide: the why of pH 7.