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Chemical Reaction Engineering problem: concentration of products is too high

Posted 31.03.2015, 08:36 GMT-4 Chemical Reaction Engineering Version 4.4 3 Replies

Mika Haber
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Hello everyone

I guess I have a simple problem but I don't know what I'm doing wrong.

When I've got a simple reaction, sth like:

x => 2z

and I enter an inital value for the concentration of x=1 mol/m^3, I have the following problem:
When comsol plots the concentration over time I get a maximal concentration of 2 mol/m^3 for z but that's impossible. The concentration of the product can't be higher than the concentration of the reagant.

How can I fix this?

Thanks for the help
3 Replies Last Post 31.03.2015, 11:30 GMT-4
Lasse Murtomäki
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Posted: 9 years ago 31.03.2015, 09:07 GMT-4
Yes it can, you have the stoichiometric coefficient 2, i.e. each x produces 2 z.
Yes it can, you have the stoichiometric coefficient 2, i.e. each x produces 2 z.
Mika Haber
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Posted: 9 years ago 31.03.2015, 09:48 GMT-4
Hi Lasse,

thank you for your reply.

I think I had an understanding problem. I thought the maximum concentration could only be 1 mol/m^3 if thats the concentration of the reagent. But it makes sense, that the concentration of z is 2 times because for 1 molecule x there will be two z, if I understood it correctly.

I appreciate your help.

br
Hi Lasse, thank you for your reply. I think I had an understanding problem. I thought the maximum concentration could only be 1 mol/m^3 if thats the concentration of the reagent. But it makes sense, that the concentration of z is 2 times because for 1 molecule x there will be two z, if I understood it correctly. I appreciate your help. br
Lasse Murtomäki
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Posted: 9 years ago 31.03.2015, 11:30 GMT-4
Mass of the material does not naturally change, but in chemistry we are counting mols that are not absolute in the sense that when talking about them you have to define which compound you are talking about. Yet, mol is needed because substances react in integer ratios of mols.
Mass of the material does not naturally change, but in chemistry we are counting mols that are not absolute in the sense that when talking about them you have to define which compound you are talking about. Yet, mol is needed because substances react in integer ratios of mols.

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