Michel Jullian wrote: > > Fred I really meant "the reaction below", H2 combustion in O2: > > 2 H2 + O2 ----> 2 H2O >
Gibbs Free Energy from CRC tables. HOH - 56.687 (liquid) OH + 8.18 HO-OH - 28.78 H +48.58 H2 0.00 O + 55.39 O2 0.00 2 H2 (g) + O2 (g) -----> 2 H2O (liquid) 2 times -56.687 Kcal/mole or 2 x KJ/mole = - 475 KJ Gibbs Free Energy for combustion of 2 moles of H2 at STP. Measured innumerable times in a bomb calorimeter. > > How many joules per mole does this produce, and does this correspond to the > enthalpy change or to the Gibbs free energy change of the reaction? > > The question is only intended to solve the controversy one way or another, I > haven't looked up the answer. Admittedly I have my own opinion of what it > will be (enthalpy), so in this sense you can call it a trick question. > > Michel > > ----- Original Message ----- > From: "Frederick Sparber" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Saturday, June 03, 2006 3:53 PM > Subject: Re: Free Radical Chain Reactions > > > > Michel Jullian wrote: > >> > >> BTW Fred, have you given some thought to our enthalpy vs Gibbs > > controversy? > >> Which energy can be recovered from the reaction below do you think, the > >> enthalpy change or the Gibbs free energy change? > >> > > Is that a trick question, Michel? > > > > The H-H bond is 498 Kjoule/mole the same as the O-O bond and the O-H > > bond.. > > Hence overall, H-H + O-O ----> H-O-H + O nets Zip Gibbs or Enthalpy. > > But, O + Fe ---> Fe-O: Fe-O (390 KJ/mole) minus Fe-Fe (100 KJ/Mole) > > equals a Gibbs Free Energy of 390-100 = 290 KJ when you oxidize iron > > with O radicals. :-) > > > > OTOH, H-O-H 2 x 498 KJ/Mole + Ni ----> NiO (382 KJ/mole) + > > H-H = 498 - 382 = 116 KJ/mole. Easy to Compare Enthalpy > > with the Ellingham (enthalpy) Diagrams. > > > > http://www.chem.mtu.edu/skkawatr/Ellingham.pdf > > > > Fred. > >> > >> Michel > >> > >> ----- Original Message ----- > >> From: "Frederick Sparber" <[EMAIL PROTECTED]> > >> To: "vortex-l" <[email protected]> > >> Sent: Friday, June 02, 2006 4:52 PM > >> Subject: Re: Free Radical Chain Reactions > >> > >> > >> > Actually 2 H2 + O2 ----> 2 H2O has about 14 reaction steps. > >> > > >> > http://www.cheresources.com/reactionkinetics3.shtml > >> > > >> > "Another important consideration is the formation of chain reactions. > > The > >> > basic premise of chain reaction mechanisms is also that free radicals > > play > >> > a leading role in the destruction of reactant molecules. The chain > >> > reaction mechanism itself consists of several steps: initiation, > >> > propagation, branching (not always present), and termination. This can > > be > >> > illustrated, for certain range of temperature and pressure, by some of > > the > >> > reactions in the following Hydrogen oxidation mechanism:" > >> > > >> > "To summarize, reaction mechanisms can be assembled from elementary > >> > reactions using free radicals as the means for decomposition of the > >> > reactant, and intermediate products. Chain branching reactions, if they > >> > occur, take a very important role in the mechanism as they lead to the > >> > formation of increasing concentrations of radicals. Reaction time and > >> > temperature have a bearing on radical concentration, and the type of > >> > reaction initiating the consumption of the reactant" > >> > > > > > > >
