Menu

Discussion Forum

New Discussion
フィルター

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Combustion

Posted 2016/12/21 10:50 GMT-5 Chemical Reaction Engineering, Studies & Solvers 5 Replies

Net One
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Can anyone help?

Calculate the equilibrium composition for the reaction H2O to H2 + ½ O2 for the
ratios on n(H)/n(O) = 1.5. The temperature is 2500K, and the pressure is 3 atm.

I have done it for n(H)/n(O) = 2, which was much easier as H20 cancelled out however cannot do it with a ratio of 1.5.

Thanks
5 Replies Last Post 2016/12/22 15:18 GMT-5
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2016/12/22 2:49 GMT-5
Three variables: n(H2), n(O2), n(H2O)
Three constraints:
1. Ideal gas law for the total amount nTOT = n(H2) + n(O2) + n(H2O); p·V = nTOT·R·T
2. n(H)/n(O) = 1.5
3. Reaction equilibrium constant.

The rest is algebra. (Ideal gas law applies very well in your conditions.)

Best wishes
Lasse
Three variables: n(H2), n(O2), n(H2O) Three constraints: 1. Ideal gas law for the total amount nTOT = n(H2) + n(O2) + n(H2O); p·V = nTOT·R·T 2. n(H)/n(O) = 1.5 3. Reaction equilibrium constant. The rest is algebra. (Ideal gas law applies very well in your conditions.) Best wishes Lasse
Net One
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2016/12/22 7:04 GMT-5
How exactly do I use the equation p·V = nTOT·R·T for this since we are not given any volume.
Do I have to find the volume and if so what do I do after finding that.
Very confused with this problem. Been stuck on it for 1 week now.

Many thanks
Net One
How exactly do I use the equation p·V = nTOT·R·T for this since we are not given any volume. Do I have to find the volume and if so what do I do after finding that. Very confused with this problem. Been stuck on it for 1 week now. Many thanks Net One
Dave Greve
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2016/12/22 9:30 GMT-5
The problem you are describing is equilibrium thermochemistry. I don't have the Comsol reaction chemistry module but I have encountered this sort of problem in research on chemical vapor deposition.

This is a classic problem in chemical engineering. Briefly, if you know the standard free energy of all the species involved it's a matter of algebra. If there are only three possible components the algebra will be easy. (And you don't need a finite element application to solve).

However- at 2500 K there are lots of other possible species, sometimes present in very small concentrations. Do you care about atomic oxygen and hydrogen? Ozone? Molecular radicals?

Is this just a starting point for a chemical kinetics problem?

D W Greve
DWGreve Consulting


The problem you are describing is equilibrium thermochemistry. I don't have the Comsol reaction chemistry module but I have encountered this sort of problem in research on chemical vapor deposition. This is a classic problem in chemical engineering. Briefly, if you know the standard free energy of all the species involved it's a matter of algebra. If there are only three possible components the algebra will be easy. (And you don't need a finite element application to solve). However- at 2500 K there are lots of other possible species, sometimes present in very small concentrations. Do you care about atomic oxygen and hydrogen? Ozone? Molecular radicals? Is this just a starting point for a chemical kinetics problem? D W Greve DWGreve Consulting
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2016/12/22 11:24 GMT-5
I would take, say, 1 m3 volume.

But this is not a Comsol problem at all.

BR
Lasse
I would take, say, 1 m3 volume. But this is not a Comsol problem at all. BR Lasse
Dave Greve
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2016/12/22 15:18 GMT-5
If you want only the answer to this particular problem, use the on-line calculator

www.crct.polymtl.ca/equiweb.php
If you want only the answer to this particular problem, use the on-line calculator http://www.crct.polymtl.ca/equiweb.php

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content