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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Jayrae on October 10, 2005, 06:27:03 PM

Title: combustion of gasoline!??
Post by: Jayrae on October 10, 2005, 06:27:03 PM

Hey

my group and I are doing a project for chemistry in which we are determining the the energy efficiency and such for various vehicles, which we know how to do..however we cannot do this without the chemical equation for the cumbustion of regular gasoline (octane 87).  ???  We have looked all over the internet and through books but are unable to find it.  We realize that C8H18 is isoctane and that in order for it to be octane 87 it needs to be like 87% octane and 13% heptane or somthing but we have no idea how to use this in the equation.....Please Please help us, once we know this we can get this project rolling but until then we are really stuck!

THANK YOU!
Jen

Title: Re:combustion of gasoline!??
Post by: Borek on October 10, 2005, 06:34:36 PM

You will never find one equation for the combustion, as gasoline is a mixture of many different hydrocarbons, not only two.

However, you may try to write down equation in the general form

C_nH_2n+2 + O₂ -> H₂O + CO₂

(note it is not balanced) and add information what is the range for n for gasoline. Plus, after you will check what is average n value for gasoline (I have no idea to be honest) you may calculate mass of oxygen needed for combustion of 1 kg of gasoline.

Title: Re:combustion of gasoline!??
Post by: mike on October 10, 2005, 06:38:36 PM

2C₈H₁₈ + 25O₂ ---> 16CO₂ + 18H₂O

Title: Re:combustion of gasoline!??
Post by: mike on October 10, 2005, 06:39:41 PM

oops, sorry Borek, looks like you already posted this a second before me  :)

Title: Re:combustion of gasoline!??
Post by: mike on October 10, 2005, 06:41:13 PM

Also Jayrae, note that there is the assumption that complete combustion is taking place which is not the case in real life.

Title: Re:combustion of gasoline!??
Post by: Jayrae on October 10, 2005, 06:52:25 PM

Thanks for getting back to me so quickly guys!  Ahh i was afraid that was the case, that there was no one exact equation!  ah well we at least now we know that for sure now and have something to go from.

Thanks again!
Jen