[cimon9999]

Hi,

I'm looking to compare aluminium and gasoline as fuels. I'm aware that the reaction for gasoline is:

C8H18(l) +(25/2) O2(g) -----> 8CO2(g) + 9H2O (l) Heat of Combustion: -249.9KJ/mol

Now to make the same comparison, is the correct equation as follows?:

2Al + 3/2 O₂ --> Al₂O₃

If so, what is the heat of combustion for that equation? Is that heat of combustion also termed 'enthalpy of combustion'? Any tips on where to find the info would be much appreciated!!

Thanks,
Eamon

[shelanachium]

You seem to have a wrong figure for the heat of combustion of C8H18. Far too low!

Go to http://www.webmo.net/curriculum/heat_of_combustion/heat_of_combustion_key.html

for working out heats of combustion for organic fuels. It also shows how to get heats of combustion per unit weight and volume.

Gasoline contains mostly branched hydrocarbons whose heat of combustion is very slightly less than that of the straight-chain octane given on this site, but this will not affect your calculation significantly - especially as gasoline is a complex mixture so your result will be only approximate in any case!

Heat of combustion of Al and other elements can be found on www.periodictable.com, go for Properties.

The heat of combustion will be given per mole of atoms. Your equation for Al combustion is for TWO atoms of Al.

Calculate heat of combustion per unit weight or volume as for organic compounds.