# Comparing Decane and Octane

by 462chevelle
Tags: comparing, decane, octane
 PF Gold P: 216 So I was trying to figure some random stuff out, trying to figure out something other than gasoline to supplement inject into an engine in a stand alone with nitrous other than gasoline. I know there are a bunch of things I don't know about chemistry, but I have a couple questions before I can even proceed. I took Octane and balanced the equation and found its change in enthalpy during combustion, then I found the change in enthalpy of Decane the same way. I found Decane to have a higher change in enthalpy during combustion, please correct me if im wrong. But, i think that means that Decane has more energy per mol. Then I used a reference of -1X10^11 kJ to see how they compared for a certain amount of energy. I used the molar mass of Octane and Decane to convert these to kg used for that amount of energy. Since the molar mass of Decane is higher than Octane I found that you need less octane in kg to make this amount of energy, by quite a bit I might add. So my conclusion is that it would be a waste of time to try to use Decane. As if I even know where to find it or enough about chemistry to actually get everything working correctly. Please correct any mistakes I've made in my logic here. I'm completely self taught in Chemistry. Thanks.
 Admin P: 23,536 This is kinda unreadable wall'o'text, this post of yours. Decane having higher energy per mole looks OK, octane having higher energy per kg by quite a bit - not so. Energy per kg should be quite similar (not identical, but I would be surprised by difference of more than just a few percent).
 Emeritus Sci Advisor HW Helper Thanks PF Gold P: 6,474 The OP is what happens if you take too much caffeine while pondering the difference between octane and decane.
 PF Gold P: 216 Comparing Decane and Octane Sorry, I get a little worked up and lose all organization skills, limited on a normal day. Without my numbers in front of me octane had something like 2.8X10^6 and decane had 2.3X10^6. I attributed the different to the molar masses, octanes somewhere around 114.2 and decane somewhere around 144.4. Again, going off of memory so I could be off a few figures. And yes, I drink waaaay to much caffeine and think about stuff that is beyond my knowledge at the time of starting the thought process.