Figure 5.12 (page 225):

Fractional error in the QSSA concentration of C versus dimensionless time for the series-parallel reaction, A<-> B-> C.

Code for Figure 5.12

Text of the GNU GPL.

main.m

%% Copyright (C) 2001, James B. Rawlings and John G. Ekerdt
%%
%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License as
%% published by the Free Software Foundation; either version 2, or (at
%% your option) any later version.
%%
%% This program is distributed in the hope that it will be useful, but
%% WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%% General Public License for more details.
%%
%% You should have received a copy of the GNU General Public License
%% along with this program; see the file COPYING.  If not, write to
%% the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
%% MA 02111-1307, USA.

% This program "schm2_error.m" generates error curves for the 
% reversible series problems as the reverse rate consant and
% the second rate constant are varied.  First-order reactions

% Last edited 1/30/97.

global k1 k_1 k2

k1 = 1;


Initial = [1,0,0]';
t = [0:.01:3]';
t_tmp = t(2:length(t));

k_1 = 100;
k2 = 100;

opts = odeset ('AbsTol', sqrt (eps), 'RelTol', sqrt (eps));
[tsolver, solution] = ode15s(@rxrate,t,Initial,opts);
alpha = (k1*k2)/(k_1 + k2);
c_Css = 1-exp(-alpha*t_tmp);
c_Cexact = solution(2:end,3);
E=(c_Cexact - c_Css)./c_Cexact;
EE=abs(E);
error=log10(EE);
%answer3 = [t_tmp error];  
% JBR, 2/22/98
answer3 = [t_tmp EE];

k_1 = 1;
k2 = 1000;

opts = odeset ('AbsTol', sqrt (eps), 'RelTol', sqrt (eps));
[tsolver, solution] = ode15s(@rxrate,t,Initial,opts);
alpha = (k1*k2)/(k_1 + k2);
c_Css = 1-exp(-alpha*t_tmp);
c_Cexact = solution(2:end,3);
E=(c_Cexact - c_Css)./c_Cexact;
EE=abs(E);
error=log10(EE);
%answer3 = [answer3 error]; 
% JBR, 2/22/98
answer3 = [answer3 EE];

k_1 = 1000;
k2 = 1;

opts = odeset ('AbsTol', sqrt (eps), 'RelTol', sqrt (eps));
[tsolver, solution] = ode15s(@rxrate,t,Initial,opts);
alpha = (k1*k2)/(k_1 + k2);
c_Css = 1-exp(-alpha*t_tmp);
c_Cexact = solution(2:end,3);
E=(c_Cexact - c_Css)./c_Cexact;
EE=abs(E);
error=log10(EE);
%answer3 = [answer3 error];
% JBR, 2/22/98
answer3 = [answer3 EE];
k_1 = 1000;
k2 = 1000;

opts = odeset ('AbsTol', sqrt (eps), 'RelTol', sqrt (eps));
[tsolver, solution] = ode15s(@rxrate,t,Initial,opts);
alpha = (k1*k2)/(k_1 + k2);
c_Css = 1-exp(-alpha*t_tmp);
c_Cexact = solution(2:end,3);
E=(c_Cexact - c_Css)./c_Cexact;
EE=abs(E);
error=log10(EE);
%answer3 = [answer3 error];
% JBR, 2/22/98
answer3 = [answer3 EE];


semilogy (answer3(:,1),answer3(:,2:5));
title ('Figure 5.12')

rxrate.m

function dcdt = rxrate(t,x)
   global k1 k_1 k2
   c1 = x(1);
   c2 = x(2);
   c3 = x(3);

   r1 = k1*c1 - k_1*c2;
   r2 = k2*c2;

   dcdt = [-r1; r1-r2; r2];