Chem SAT II problem

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1

<p>Hey...this is a word problem that's been giving me a lot of trouble. I think it involves just a bunch of mole-mole conversions but I'm not sure. Anyways, here goes:</p>

<p>A car gets 9.2 kilometers to a liter of gasoline. Assuming that gasoline is 100% octane, C8H18 (which has a specific gravity of 0.69), how many liters of air (21% oxygen by volume at STP) will be required to burn the gasoline for a 1250-km trip? Assume complete combustion.</p>

<p>Thanks in advance for any help, help ASAP is greatly appreciated</p>

2

<p>well im not sure what specific gravity has to do with anything but...
1250km/9.2km/liter=135.86 liters
135.86 liters/ 22.4 mol/ liter= 6.06 mol
2C8H18 + 25O2 = 16CO2 + 18H2O
6.06 mol C8H18 *12.5 mol O2/mol C8H18 = 75.82 mol O2
75.83 mol O2 * 22.4 molO2/ liter O2= 1698.36 liter O2</p>

<p>and a question like this will never appear on the SAT test, it requires way too much calculator work</p>

3

<p>elsmurf only calculated liters of O2, but you need liters of air, so divide by .21 and the answer is 8087.28L</p>