dimensional analysis problems with simbiology mass action kinetics units

Hi,

I am tyring to build a model using reversible mass action kinetics (Matlab R2016a, Win 8.1 x64). My species units are all in molarity and I calculate the forward reaction rate units should 1/(mol/l)*second and reverse reaction units as 1/second. However, Simbiology repeatedly fails dimensional analysis when trying to run a simulation reporting that 'Quantities of different dimensions cannot be added or subtracted'.

My reactions are all quite straight forward: [A]*[B] < - > [AB] so I don't understand why this is causing such problems.

Also tried the units from the manual but still the same error.

Does anybody know how to resolve this? I have even tried randomly changing units to all possible combinations in the drop down menus and no units of concentration or mass pass dimensional analysis.

Thanks for any help.

Answer 1

[Arthur Goldsipe]

I think the problem is with the units on your forward rate constant. I think you forgot a set of parentheses and ended up multiplying by second where you want to divide by second. If you set the units to 1/(mole/liter)*second, that's the same as second/(mole/liter). I think you intended to set the units to 1/(mole/liter)/second or 1/((mole/liter)*second).

[micronaut]

thanks for the help :)

Same result with any/all combinations. I might delete the model and rebuild from scratch.

[Arthur Goldsipe]

Feel free to attach the model to a new question or to send me the model. I built a similar reaction myself and got the units to work as I described above. (Also, I don't get notified when you post a comment, so please contact me directly if it looks like I didn't see something posted here.)