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The spreadsheet did the dH algebra like it's own mentor
told it, Fred.
You could try downloading the trial version of CHEMIX
(Google it) ans see what their thermochemistry section gives for this reaction?
Mine has expired, and was in Norwegian or something for some reason (must have
missed the language option)
Michel
PS About Excel, there are other spreasheet software
around, some of which are free and claim they can read xls:
----- Original Message -----
Sent: Saturday, June 03, 2006 8:35
PM
Subject: Re: Free Radical Chain Reactions
How do they do that?
My calculations are always using dG algebra like my mentors
told me.
BTW. I don't have Excel. :-(
Fred
----- Original Message -----
Sent: 6/3/2006 12:13:36 PM
Subject: Re: Free Radical Chain
Reactions
My spreadsheet finds at 25° and
1atm:
|
O2(g) + 2 H2(g) -> 2 H2O(l) + 571.66 kJ/mol
(exothermic) |
|
|
|
|
|
|
Spontaneous at 25°C. Equilibrium at about
1477°C. |
|
|
|
|
|
|
Molar masses and thermodynamic properties |
Enthalpy change kJ/mol |
Entropy change J/K/mol |
Gibbs Free Energy change kJ/mol |
|
Sources: c.f. bottom of spreadsheet |
-571.66 |
|
-326.69 |
|
-474.31 |
|
Again I agree with your dG value as you
can see at bottom right of the above table, but I suggest innumerable
calorimeters have measured a thermal energy of 572 kJ/mole
(enthalpy) rather than 474 or 475 kJ/mole (Gibbs)
Michel
----- Original Message -----
Sent: Saturday, June 03, 2006 7:42
PM
Subject: Re: Free Radical Chain Reactions
> 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 -5! 6.687 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: <vortex-l@eskimo.com&g!
t;
&g t;> 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" <vortex-l@eskimo.com>
>> >> Sent: Friday, June 02, 2006 4:52 !
PM
&g t;> >> 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"
>> >>
>>
>
>> >
>> &g! t;
>>
>
>
> <
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