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From: Torsten Hennig <Torsten.Hennig@umsicht.fhg.de>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Newton Raphson method for chemical equilibrium system
Date: Wed, 04 Aug 2010 10:55:44 EDT
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Xref: news.mathworks.com comp.soft-sys.matlab:658998

> 
> Thanks Steve, but I can't read German.  I'm trying to
> solve the following system of equations:
> where: CH4 = N(1), H2O = N(2), CO = N(3), H2 = N(4),
> CO2 = N(5), O2 = N(6)
> 
> CH4+CO+CO2-C = 0
> 4*CH4+2*H2O+2*H2-H = 0
> H2O+CO+2*CO2+2*O2-O = 0
> -LnKp1+2*log(P/sum(N))+log(N(3))+3*log(N(4))-log(N(1))
> -log(N(2)) = 0
> -LnKp2+log(N(5))+log(N(4))-log(N(3))-log(N(2)) = 0
> -LnKp3-0.5*log(P/sum(N))+log(N(2))-log(N(4))-0.5*log(N
> (6)) = 0 
> 
> Known inputs are LnKp, C, H, O.  Where LnKp is the
> log of the equilibrium constant for that particular
> reaction at the specified temperature.

The first thing I'd do is to substitute N(i) = N~(i)^2
for i=1,...,6 to avoid negative arguments within
the logarithm.

Best wishes
Torsten.