(changed the subject line again to confuse you further Fred ;) Fred wrote: >> So here is CHEMIX's thermochemistry answer for the reaction we discussed >> (copy-paste): >> >> 2H2(g) + O2(g) = 2H2O(l) + 571.6kJ >> >> which solves the controversy (produced energy is equal to -dH=572kJ/mol, > not >> to -dG=474kJ/mol), doesn't it Fred? :))) >> > I'm not sure, Michel. The heat of formation from the elements dH is > 2 x 498,000 for 2 H2 molecules from 4 H atoms and 498,000 for an O2 > molecule > from 2 O atoms. > Then you have to break 3 x 498,000 = 1.49E6 kJ to form 2 H2Omolecules > from 4 H atoms + 2 O atoms ---> H-O-H + H-O-H (4 x 498 kJ) - (3 x 498 kJ) > = 498 kJ > > Which implies that 571.6 kJ - 498 kJ = 73.6 kJ is the heat given up > by the two H2O molecules when cooled from a hot gas to liquid H2O > in the calorimeter???.
_Moles_ of atoms/molecules you mean Fred. Yes that's about it. Had you used more accurate bond energies, instead of 73.6 kJ you would have found 88 kJ, i.e. twice the water condensation energy 44kJ per mole of H2O (1 mole of H2O = 18g = 6.02*10^23 molecules of H2O) Controversy solved? Michel
