Combustion Equations: Converting kg to kmol & KJ/Kmol to KJ/Kg

[skaboy607]

Hi,

I am learning about the above at the moment and was wondering when the reaction equations are given or you have worked these out, are they in kg or kmol. I have looked at mixtures and know how to go between the two when given the ultimate or gravimetric analysis but am unsure when I have just the reaction equation.

Also, when dealing with enthalpy of combustion, it is given from steam tables as KJ/Kmol, if wanted to convert this to KJ/Kg, how would I do this. Again from mixtures, I have been trying to do mols multiplied by molecular weight, but this hasn't been giving me the answer I want.

Any help much appreciated.

Thanks

 

[xxChrisxx]

I'm assuming you mean the chemical combustion equation. All chemical equations are given in moles so simply balance them (for stoichiometric). You can then convert each species to its gravimetric weight.

For the enthalys just work in moles its far easier.

I strongly suggest you buy/borrow/steal
Paul Heywood - ICE fundamentals
Richard Stone - Introduction to ICE.

as they contain simply everything you would ever need to know regarding engines.

 

[skaboy607]

Thanks for your clearing that up for me; I will look into obtaining those books.

With regards to the enthalpies, what if needed to have convert them into kj/kg, how would I go about it?

Thanks

 

[jaap de vries]

For a more general combustion backgound I would recommend "an introduction to combustion" by Stephen Turns (Penn State)

Chriss is right most tables are given on a molar basis. Be careful when using tables from different books because some may have different reference values.