Energy content of gasoline and hydrogen comparative math question

  • #26
haruspex
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So 1 gallon of gasoline contains 36,315 g of Carbon which will produce 70 g of CO2 but then what?
12g of C produce 44g CO2, remember? So many g of CO2 will 36,315 g of Carbon produce?
 
  • #27
12g of C produce 44g CO2, remember? So many g of CO2 will 36,315 g of Carbon produce?
Would I just divide these two?
 
  • #28
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Would I just divide these two?
12g of C produce 44g CO2.
So 1g of C produces .. how many g of CO2?
So 36,315 g of Carbon produce.. how many g of CO2.?
 
  • #29
12g of C produce 44g CO2.
So 1g of C produces .. how many g of CO2?
So 36,315 g of Carbon produce.. how many g of CO2.?
When I did this as a ratio I got 133,155 g of CO2 but thats still not the answer in the back of the book is there another step?
 
  • #30
haruspex
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When I did this as a ratio I got 133,155 g of CO2 but thats still not the answer in the back of the book is there another step?
Yes, you haven't used the final ratio: 70g CO2 corresponds to 1MJ energy.
If 1 gal gasoline releases 133,155 g of CO2, and each 70g CO2 indicates 1MJ of energy, how many MJ for the whole gallon?
 
  • #31
Yes, you haven't used the final ratio: 70g CO2 corresponds to 1MJ energy.
If 1 gal gasoline releases 133,155 g of CO2, and each 70g CO2 indicates 1MJ of energy, how many MJ for the whole gallon?
When I did this I got 1902.214 MJ. Is this right?

If so how would I go about doing part B?
 
  • #32
Wait I realized that is only for 1 gallon so I got 28530 MJ
 
  • #33
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When I did this I got 1902.214 MJ. Is this right?
that is only for 1 gallon so I got 28530 MJ
Right!
If so how would I go about doing part B?
This is much easier. you have 15 gals at 12.8 MJ/m^3.
 
  • #34
Right!

This is much easier. you have 15 gals at 12.8 MJ/m^3.
I don't understand what this means though? Is this all the information I need?
 
  • #35
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I don't understand what this means though? Is this all the information I need?
The only other information you need is how to convert US gallons to m3. Look it up.
 
  • #36
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Yes. So you have, for burning gasoline:
  • 12 atomic masses C corresponds to 44 atomic masses CO2
  • 70g CO2 corresponds to 1MJ energy
  • 1 gallon gasoline corresponds to 36,315 g C
So how many J energy correspond to 1 gallon gasoline?
This is incorrect. According to the attachment in Post #4, 1 gallon of gasoline has a carbon content of 2421 g, not 36,315 g. The latter figure is for 15 gallons of gasoline.
 
  • #37
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This is incorrect. According to the attachment in Post #4, 1 gallon of gasoline has a carbon content of 2421 g, not 36,315 g. The latter figure is for 15 gallons of gasoline.
Well spotted - thanks. But fortunately courtneywetts used the right ratio later.
 

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