## Modeling Chemical Reactions.......?

### Vikram (view profile)

on 6 Apr 2011
Accepted Answer by Wikke den Hartogh

### Wikke den Hartogh (view profile)

Hi everyone.I am not so familiar with MATLAB or programming.I am writing a code for Solar Model.As a part of it i need to model some chemical reactions.

Ex:

`            p     +    p  -------->  D   +  (e^+)  +  neutrino`
`            D     +    p  -------->  3He +   photons`

Will it be possible? If yes, how?

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### Wikke den Hartogh (view profile)

on 7 Apr 2011

Modeling chemical reactions is not very difficult.

first, rewrite the chemical reaction as a differential equation.

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example for reaction A->P (with rate constant 'k1')

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Rate equation: Ra=-k1*Ca

ODE: dCa/dx = -Ra (x either being time or axial position in a PFR)

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Now you can solve this with an ordinary ODE-solver.

#### 1 Comment

Wikke den Hartogh

### Wikke den Hartogh (view profile)

on 7 Apr 2011

sorry, there shouldn't be a minus in front of Ra in the ODE, all depends on your reactions. One more thing, at which point Matlab comes in handy, you can model whatever number of reactions you want, and solve them as a system of ODE's. you're system consists of two consecutive reactions, this can be modelled without any problem.

### the cyclist (view profile)

on 6 Apr 2011

Yes, it is possible to model this in MATLAB. But I really don't think it is possible to teach you programming and MATLAB from scratch, via this forum. Sorry.

Vikram

### Vikram (view profile)

on 6 Apr 2011

hey thanku for ur response.......
plz just gime the basic idea.i'll try the rest.

### John D'Errico (view profile)

on 6 Apr 2011

In order to build a model, one needs to know what your goal is, what you will do with that model. Only you know those things, and you have not communicated them to the world. Perhaps the solution is a differential equation system. Perhaps it is a simple formula. (I'm not a chemist, so I can't go too far here.)

Often your goals for the model drive the solution. Is this something you need to model as a function of time? If so, then often differential equation models are good choices. But you will then need to write down the equations. Transform the graphical form you wrote into mathematics. Then the MATLAB code will naturally be easier.