Trevor asked in Science & MathematicsChemistry · 1 month ago

# how many grams of oxygen are required to react with 18.0 grams of octane (C8H18) in the combustion of octane in gasoline?

Update:

I already balanced the equation just need to know the answer. Really bad at figuring it out

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• 1 month ago

Stoichiometry .....

Really bad?  If you learn how to use the unit-factor method of problem solving (aka dimensional analysis) then you will be a whiz at doing stoichiometry problems.  It will be nearly impossible to make a mistake.

2C8H18(g) + 25O2(g) --> 16CO2(g) + 18H2O(g)

18.0g ............. ???g

18.0g C8H18 x (1 mol C8H18 / 114.0g C8H18) x (25 mol O2 / 2 mol C8H18) x (32.0g O2 / 1 mol O2) = 63.2g O2

But the actual answer is nearly ZERO.  That's because there is essentially no octane (C8H18) in gasoline.  It comprises less than 1% of the mixture we call gasoline.  Just because there is an "octane rating" for gasoline doesn't mean that gasoline contains octane.

The "octane rating" doesn't even use n-octane.  It uses 2,2,4-trimethyl pentane (C8H18), called "iso-octane", and n-heptane.  The rating is the percentage of 2,2,4-trimethylpentane in a mixture of it and heptane that performs like the test gasoline.