# Energy content of gasoline and hydrogen comparative math question

haruspex
Homework Helper
Gold Member
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?

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?

haruspex
Homework Helper
Gold Member
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.?

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?

haruspex
Homework Helper
Gold Member
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?

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?

Wait I realized that is only for 1 gallon so I got 28530 MJ

haruspex
Homework Helper
Gold Member
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.

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?

haruspex
Homework Helper
Gold Member
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.

SteamKing
Staff Emeritus
Homework Helper
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.

haruspex