How to iterate xa from 0 to 1 with steps of 0.05 in the function r=F*(k*C*(​1-xa))/(1+​K*C*(1-xa)​). All variables are known except for r.

I have to iterate the conversion of a reaction (x) in order to get the different values of catalyst mass (m).

The conversion 'x' would go from 0 to 1 with spaces of 0.05.

The function I need to iterate is: m=F*(k_kin*C*(1-x))/(1+k_ads*C*(1-x))

I know the value of all the variables except for m, which is the mass that I'd like to calculate.

F=0.11574; k_kin=1.3*10^-6; C=1.086; k_ads=0.9986

Please, help me. I haven't used matlab in years and I've forgotten how to make a 'for' loop work.

Thank you in advance.

[madhan ravi]

Urgent

Answer 1

[Star Strider]

Everything except ‘x’ are scalars, so you can do this using a vectorization approach without the loop:

F=0.11574; k_kin=1.3*10^-6; C=1.086; k_ads=0.9986;
x = 0:0.05:1;
m=F*(k_kin*C*(1-x))./(1+k_ads*C*(1-x));

figure
plot(x, m)
grid
xlabel('Reaction')
ylabel('Catalyst Mass')

... including the plot! (Note the (./) denoting element-wise division.)

[Marina Gonzalez]

Thank you! I have the same problem I had before. I'm doing something wrong because the plot is not right, but at least now I know how to write it down.

Thank you again!

[Star Strider]

As always, my pleasure!

Answer 2

[Geoff Hayes]

Marina - try

m = zeros(20,1);
k = 1;
for x = 0:0.05:1
    m(k) = F*(k_kin*C*(1-x))/(1+k_ads*C*(1-x))
    k = k + 1;
end

edit to above: repalce == with = in assignment to m

[Marina Gonzalez]

It gives me this error:

Index exceeds the number of array elements (20).

Error in Untitled (line 12)

m(k) == F*(k_kin*C*(1-x))/(1+k_ads*C*(1-x))

[madhan ravi]

m = zeros(numel(x),1);
for k = 1:numel(x)
    m(k) = F*(k_kin*C*(1-x(k)))/(1+k_ads*C*(1-x(k)))
end

And Ofcourse if you change / to ./ you don’t need a loop.

[Marina Gonzalez]

It is working, but it only gives me one value of m. I'd like every value of m for each x. How can I do that?

[Geoff Hayes]

Are you sure that you are updating the m array on each iteration of the loop?

[Marina Gonzalez]

This is everything I have written:

F=0.11574;

C=1.086;

k_ads=0.9986;

k_kin=1.3*10^-6;

m = zeros(numel(x),1);

for k = 1:numel(x)

m(k) = F*(k_kin*C*(1-x(k)))/(1+k_ads*C*(1-x(k)))

end

plot(x,m,'r')

[madhan ravi]

plot(x, F*(k_kin*C*(1-x))./(1+k_ads*C*(1-x)))

[Geoff Hayes]

where is x defined? I think you are missing

x = 0:0.05:1;

just prior to where you define m.

[Marina Gonzalez]

Thank you! That has really helped. I think I'm doing something wrong because for a conversion of 0, the mass of the catalyst is way bigger than for the total conversion.

I'm doing something wrong but I don't know what. I'll think about it.

Thank you once again!

Answer 3

[Marina Gonzalez]

It's me again- sorry!

What if the function instead of being the one I said before was m(k) = F*(1+k_ads*C*(1-x))/(k_kin*C*(1-x))

Would anything change? Because when I plot this new equation nothing shows up on the graph

[Star Strider]

It shows up when I plot it!

Try this:

F=0.11574; k_kin=1.3*10^-6; C=1.086; k_ads=0.9986;
x = 0:0.05:1;
m = F*(1+k_ads*C*(1-x))./(k_kin*C*(1-x));

figure
plot(x, m)
grid
xlabel('Reaction')
ylabel('Catalyst Mass')

Remember to use element-wise division (./).

[Marina Gonzalez]

Thank you sooooo much! It works! You've saved my day! :)

[Star Strider]

As always, my pleasure!