Help with stoichiometry? Any braniacs?

Question

My car has a 13.7 gallon tank. Assuming that gasoline is entirely made from octane(C8H18), how many POUNDS of CO2 would be froduced from my car each time I use a tank of gas? How many pounds of CO2 will produce from my car each year(I drive 21,500 miles each year)?
Some equalities you may find useful
- 1 lbs- 4536 kg
1 kg-2.205 lbs.
28.35g-3.785 liters
l inch-2.54 cm
density of octane-.855g/ml
my car averages 29.7 miles/gallon

use the following equation
C8H18 + 12 1/2 O2 --> 8 CO2 + 9H2O
if u can find the answer and show work, it would be greatly appreciated. Please hlp. thx It would be nice if u can show step by step using factor labeling or something. Please show work

Answer 1

I assume that should be 1 gal = 3.785 liters.
13.7 gal = 51.85 L
Mass of octane = 51.85(0.855) = 44.34 kg.
Octane has formula mass 8*12.0 + H18*1.0 = 114.0. So the number of moles is (4.434 * 10^4 / 114.0 = 388.9 mol.
n(CO2) = 8n(C8H18) = 8(388.9) = 3111.3 mol.
CO2 has formula mass 12.0 + 2 * 16.0 = 44.0. So the mass of CO2 is 3111.3 * 44.0 = 1.369 * 10^5 g = 136.9 kg
= 136.9 * 2.205 = 302 pounds (3 sf).

Driving 21,500 miles at 29.7 miles/gallon will use 21500/29.7 = 723.9 gallons of gas. This equates to 723.9 / 13.7 = 52.84 tanks, so the CO2 produced will be 52.84 * 302 = 1.60 * 10^4 pounds (3 s.f.).

Answer 2

here's what i got.

(if there are values with a divison between them ex: (16 CO2 / 2C8H18) put them over eachother ex 16 CO2 over 2C8H18 X 44.011g CO2 over 1 mol. to see it all more clearly. if you need a different format, email me.)

2C8H18 + 25O2 --> 16CO2 + 18 H2O

( 13.7 g C8H18 / 1 ) X ( 1 mol C8H18 / 114.232g ) X ( 16 CO2 / 2C8H18 ) X ( 44.011g CO2 / 1 mol ) =

9647g CO2 / 228.464 = 42.266g CO2

42.226g CO2 X ( 453.6 g / lb ) = *****0.9309 lbs CO2 per tank*****

(29.7 mi/gal) X 13.7 (gal/tank) = 406.89 mi/tank

(21500mi/year) X (406mi/tank) = 52.8398 tank/year

(0.9309 lbs/tank) X (52.8398 tank/year) = ***49.1886 lbs CO2 per year***

Hope that helps

I'm only a sophomore in HS chemistry not a chemistry major, so no promises, but we've been doing problems like this all year. if you have any questions, email me at [e-mail] and i can send it to you in a word document where the format is better.

Answer 3

I can't work with gallons.. sorry.