Quote:
Originally Posted by andestang
This doesn't make sense. Octane is not a compound, it's a measurement. The octane rating is "a measurement of the resistance of petrol fuels to auto-ignition in spark-ignition internal combustion engines". Octane rating does not relate to the energy content of the fuel, it is only a measurement of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Ethanol is basically an alcohol ( biologically produced)and by itself can have an octane rating of 110 or higher, but its heating value lacks (the energy released as heat). And for fuel economy you will not get the mileage that FFV's will get running on Ethanol. Hope this makes more sense.
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Ahh, well I understood the 'Octane Rating' incorrectly then... however, "Octane Rating" is obviously not a compound, but "Octane" IS a molecular compound. C8H18... Ethane, C2H6, is the hydrocarbon comparable to Ethanol (an alcoholized Ethane Molecule), Ethanol > C2H5OH. (Note the addition of 1 oxygen molecule between a hydrogen and the carbon bases). Anyways... that doesnt matter about the octane rating... since I didnt understand that part... but the energy contained per unit (in combustion) is higher in a molecule of true "Octane"(C8H18) which IS a component in gasoline, than it is in Ethanol (C2H5OH), the reason being that there are more available C-H bonds to break in octane (per molecule, so more energy released per mole), than in Ethanol.
Yeah, the control of energy release is more ordered (I remember learning about that now), but im simply stating that (as you stated) the amount of heat energy released is lower because of the lesser bonds.
Cheers,
Chris
(and thanks for the info about octane rating!)