Re: oxalic acid

[Paul Sears <psears at nrn1_NRCan.gc.ca>]

> From: "roger" <roger at spinn_net>
> Subject: re:  Oxalic Acid
> 
> Paul Sears wrote:
> 
> > Does anyone have a number for the standard electrode potential
> > for oxalate/CO2?
> 
> I don't, but my old CRC Handbook gives the standard free energy of formation
> for oxalate ion and CO2 as -161.3 kcal/mole and -92.31 kcal/mole,
> respectively.  From that the standard free energy for the reduction of CO2 to
> oxalate ion:
> 
> 2(CO2) + 2e- -> 2(OOC-COO)-2
> 
> is +23.32 kcal/mole.  The corresponding standard reduction potential is +0.5
> volts.

	It doesn't work that way.  The H+  +  e-  ->  1/2 H2  half cell
reaction is _defined_ as having a zero standard electrode potential,
so to go from free energies to standard potentials, we need the free
energy of reaction of the complete cell,  oxalate/CO2 on one side
and H+/H2 on the other.  The complete cell reaction would be:

	H2 + 2CO2  ->  H2C2O4(solution)

	The free energy of _that_ reaction would give you the standard
potential.

> Good luck.  Either yeast and sugar or bottled gas seems much easier.

	I agree, but I'm glad to see some experimentation going on.

-- 
Paul Sears        Ottawa, Canada