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

• skaboy607
In summary, the conversation is about learning about chemical combustion equations and how to convert between moles and gravimetric weights. It is recommended to use books such as "ICE fundamentals" and "Introduction to ICE" for more information. To convert enthalpies from KJ/Kmol to KJ/Kg, it is suggested to use the book "An Introduction to Combustion" by Stephen Turns, and to be cautious of reference values when using tables from different sources.
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

Last edited:
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.

Paul Heywood - ICE fundamentals
Richard Stone - Introduction to ICE.

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

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

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.

## 1. What is a combustion equation?

A combustion equation is a chemical equation that shows the reactants and products of a combustion reaction. It represents the conversion of a fuel source, such as a hydrocarbon, into carbon dioxide and water, along with the release of energy in the form of heat and light.

## 2. What is the importance of converting kg to kmol and KJ/Kmol to KJ/Kg in combustion equations?

Converting between mass units (kg) and molar units (kmol) is important in combustion equations because it allows for a more accurate representation of the amount of fuel being used and the amount of energy being released. Similarly, converting between energy units (KJ/Kmol and KJ/Kg) allows for the comparison of different fuels based on their energy content.

## 3. How do you convert kg to kmol in combustion equations?

To convert from kg to kmol, you need to know the molar mass of the compound being used as a fuel. This can be calculated by adding the molar masses of each element present in the fuel source. Once you have the molar mass, you can divide the given mass in kg by the molar mass to get the amount in kmol.

## 4. How do you convert KJ/Kmol to KJ/Kg in combustion equations?

To convert from KJ/Kmol to KJ/Kg, you need to know the molar mass of the compound being used as a fuel. Once you have the molar mass, you can divide the given energy value in KJ/Kmol by the molar mass to get the energy value in KJ/Kg. This conversion allows for the comparison of different fuels based on their energy content per unit mass.

## 5. How do combustion equations contribute to our understanding of energy and fuel usage?

Combustion equations play a crucial role in understanding the conversion of fuel sources into energy. By accurately representing the reactants and products of a combustion reaction, these equations allow us to calculate the amount of energy released and compare different fuels based on their energy content. This information is important for making informed decisions about fuel usage and energy consumption.

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