Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Mahirt on July 04, 2013, 11:01:38 AM

Title: Need help solving a combustion equation
Post by: Mahirt on July 04, 2013, 11:01:38 AM
Hi can anyone help me solve this combustion equation that will be carried out in air. LiClO4 + C2H6O2 + C15H10N2O2 + Al =?? .. The fuel is Al,, C2H6O2 and C15H10N2O2 are also considered part of the fuel but their main functions are to be binder/polyol/dissolver and LiClO4 is the oxidiser (Which is what will be dissolved) . Later I plan to try LiClO4 +NH4ClO4 + C2H6O2 + C15H10N2O2 + Al.... In that case both LiClO4 +NH4ClO4 are oxidisers..  Thanks.
Title: Re: Need help solving a combustion equation
Post by: Borek on July 04, 2013, 11:22:15 AM
Your equation looks way too high energetic to my liking, but let's just concentrate on the stoichiometry.

It is a mixture - and there is no such thing as a single reaction equation for a mixture, in which separate things react separately.
Title: Re: Need help solving a combustion equation
Post by: curiouscat on July 04, 2013, 12:05:29 PM
Your equation looks way too high energetic to my liking, but let's just concentrate on the stoichiometry.

Perhaps he's a propellent designer.  ;D
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 04, 2013, 01:12:08 PM
I dont necessarily need the end products I actually need the ratio that will allow complete combustion of all reactants.. Once I find that I will probably have to attempt finding the rest experimentally. Stoichiometry will help me reach that but im not sure how to begin.
Title: Re: Need help solving a combustion equation
Post by: Arkcon on July 04, 2013, 01:36:01 PM
Well, lets try to start.  You say aluminum is the fuel, and lithium perchlorate is the oxidizer.  Let's try to balance that reaction.  The binders will also have to be consumed before all of the aluminum can react, so you should write and balance those reactions as well.
Title: Re: Need help solving a combustion equation
Post by: Borek on July 04, 2013, 01:50:28 PM
I dont necessarily need the end products

Yes you do. You can't do the stoichiometry without knowing what the reaction is.
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 04, 2013, 02:53:43 PM
I got this for the oxidiser with the fuel alone.. 3LiClO4 + 8Al = 4Al2O3 + 3LiCl..
Title: Re: Need help solving a combustion equation
Post by: Borek on July 04, 2013, 04:12:40 PM
That's a good starting point.

You have 8 moles if Al reacting with 3 moles of lithium perchlorate. Convert moles to masses and you have your weight ratio.
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 05, 2013, 09:07:45 AM
Ok but when I try to do the rest I get stuck..
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 05, 2013, 02:26:30 PM
The binder part of the equation I mean..
Title: Re: Need help solving a combustion equation
Post by: Borek on July 05, 2013, 02:36:39 PM
Have you tried to balance their combustion reactions?
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 05, 2013, 07:34:17 PM
Problem is I dont know the products of the rest of the equation..
Title: Re: Need help solving a combustion equation
Post by: Arkcon on July 05, 2013, 08:18:31 PM
Problem is I dont know the products of the rest of the equation..

This can be hard to figure out, but you can try to make educated guesses.  You know that aluminum oxidizes to aluminum oxide, so what will carbon hydrogen and nitrogen, um ... and oxygen ... um oxidize into?
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 06, 2013, 02:09:03 PM
I guess that water and Aluminium oxide will form. As for the rest I dont know..
Title: Re: Need help solving a combustion equation
Post by: curiouscat on July 06, 2013, 02:15:42 PM
I guess that water and Aluminium oxide will form. As for the rest I dont know..

Probably some CO2 and NOx as well.

What Cl will end up as is interesting. HCl? ClO2?
Title: Re: Need help solving a combustion equation
Post by: Mahirt on July 06, 2013, 03:24:36 PM
it will become LiCl.. When using AP as the oxidiser it turns to HCl
Title: Re: Need help solving a combustion equation
Post by: Arkcon on July 06, 2013, 05:21:49 PM
So you're sure that lithium chloride is in the exhaust?  I'd defer my opinion to your knowledge of the subject, but it seems odd to me for an ionic salt to be present in hot exhaust fumes.  Maybe some other reaction occurs afterward?  Lithium oxide seems more refractory to me, and more like smoke particles.
Title: Re: Need help solving a combustion equation
Post by: curiouscat on July 06, 2013, 11:20:11 PM
So you're sure that lithium chloride is in the exhaust?  I'd defer my opinion to your knowledge of the subject, but it seems odd to me for an ionic salt to be present in hot exhaust fumes.  Maybe some other reaction occurs afterward?  Lithium oxide seems more refractory to me, and more like smoke particles.

Lithium Chloride just might be more stable than Lithium Oxide. I know F containing rocket oxidizers exploited a similar principle.