Arguably, the bond energy shown in kcal should be shown in J or a derivative, since J is SI and kcal is not.
--22.214.171.124 20:04, 26 April 2006 (UTC)
Dissociation energy too low?
If the dissociation energy is as low as 3.4 kJ/mol, what acounts for the high heat of vaporization of 40 kJ/mol? Dan Gluck 17:29, 19 June 2007 (UTC)
Because water is actually much more complex. There are monomers, dimers, trimers, teramers, ion-pairs etc. these all add up. Some break when transitioning to the gas phase, some don't there is no simple answerPedroDaGr8 (talk) 02:40, 29 October 2008 (UTC)
The ab initio binding energy between the two water molecules is estimated to be 5-6 kcal/mol, although values between 3 and 8 have been obtained depending on the method. The experimentally measured dissociation energy (including nuclear quantum effects) of (H2O)2 and (D2O)2 are 3.16 ± 0.03 kcal/mol (13.22 ± 0.12 kJ/mol) and 3.56 ± 0.03 kcal/mol (14.88 ± 0.12 kJ/mol), respectively. The values are in excellent agreement with calculations.
Is the "ab initio binding value" in the first sentence the same as the value obtained by "calculations" in the third sentence? If so, does that mean that I should consider 3.16 and 3.56 to be in excellent agreement with 5-6, for this kind of calculation?
Is the "binding energy" the same as the "dissociation energy"?
Why do nuclear effects play a role, other than the mass of the nucleus (I realize this last question is beyond the scope of the article)? — Preceding unsigned comment added by 126.96.36.199 (talk) 18:37, 12 January 2015 (UTC)
Nuclei effects (i.e. changing H to D) alter the zero-point energy (ZPE). I think "The ab initio binding energy" refers to the difference between the minimum of the curve and the energy at dissociation (i.e. no ZPE). The calculations will combine the binding energy with the ZPE. --Bduke (Discussion) 22:07, 12 January 2015 (UTC)