----- Original Message -----
From: "Frederick Sparber" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, May 17, 2006 9:46 AM
> I'm after that ~ 80,000 joule/mole Spontaneous Free Energy in the
> Autoionization of Water
> ( 0.83 eV per H-OH bond, 2 H2O <---> H3O+ + OH -)
Fred do you mean the following? (H3O+ is the aqueous solute of H+ isn't
it?
My chemistry courses are awfully far away :)
---------
H2O(l) -> OH-(aq) + H+(aq) - 55.836 kJ/mol (endothermic)
Reverse reaction spontaneous at 25°C. No equilibrium temperature.
--------
If it is then it's about 60kJ/mol but absorbed, not produced, and it only
occurs in a marginal way (not spontaneous at any temperature)
http://chimge.unil.ch/En/ph/1ph4.htm
"2 H2O <---> H3O + + OH- delta G = 79,900 joule/mole"
Oh you meant the Gibbs free energy change Fred? My spreadsheet agrees: it
finds dG=79.87 kJ/mol for the reaction as I have written it, so it's
obviously the same reaction.
But dG has nothing to do with produced energy, which is -dH (minus the
_enthalpy_ change), which in the present case is negative (-56kJ/mol as
shown above i.e. the reaction absorbs energy). dG is about spontaneity and
dynamics, not about net energy. If you're interested in the thermochemistry
calculator spreadsheet which can work out this kind of stuff (enthalpies,
entropies, Gibbs, and more) for any reaction you specify, I'll send it to
you by private email.
Michel
In running closed cell Conductivity-Resistivity tests of water with inert
electrodes
the values stay constant, Michel. :-)
Fred
