Chemical Forums
Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: Heater on September 24, 2024, 01:39:04 PM
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I have an assigenment where i need to calculate the lover heating value of the combustion of 100 mol of a gas mixture (MJ/Nm3)
The gas mixture is made of in mol%:
91.1% CH4
4.7% C2H6
1.7% C3H8
1.4% C4H10
0.6% N2
0.5% CO2
the enthalpy of the combustion reaction of methane, ethane, propane and butane, are given:
Methane combustion : -804,2 kJ/mol
Ethane combustion : -1428,9 kJ/mol
Propane combustion : -2045,5 kJ/mol
butane combustion : -2663.6 kJ/mol
we are also told the gasmixture behaves like an idealgas.
The solution in the book is given to be 38,8 MJ/m3 but i can't seem to get the right answer no matter what i do.
my main theory to calculating it was to calculate the ΔH of the combustion reaction using the enthalpy of the 4 gas combustions given by adding them together and multiplying with their respective mol% and then dividing it with the normal volume of an idealgas 22,42 m3/kmol which gives me a solution of 38,93 MJ/M3 which is close to the solution but not quite it.
Does anyone know how what i am missing?
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Calculate how many m^3 is 100 mol
Then calculate each ΔH value . Get summary and division through the volume.
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the enthalpy of the 4 gas combustions given by adding them together and multiplying with their respective mol% and then dividing it with the normal volume of an idealgas 22,42 m3/kmol which gives me a solution of 38,93 MJ/M3 which is close to the solution but not quite it.
I did the same and got 38.897 MJ/m3 (so more like 38.90).
Approach is correct, I would assume this is just a typo (or lousy rounding) in the answer key.