Gasoline/energy question PLEASE HELP

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In summary, more energy is stored in octane than in methanol, and methanol will require a larger tank.
  • #1
sciencenerd
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gasoline/energy question...PLEASE HELP!

This is one of the problems i have to do...COMPLETELY LOST on it. I don't even know where to start or what to do. Please, please, please could someone help??

One of the serious problems that we have not yet solved is the use of fossil fuels, especially gasoline, to power our automobiles. Companies around the world are constantly trying to find a suitable replacement for gasoline. If we use octane (C8H18) as the representative of what is contained in gasoline, and compare it to methanol (CH3OH), currently a promising substitute for gasoline, what will be the energy difference on a per gram basis for the two. For the reaction of octane with oxygen to produce carbon dioxide and water, 48.1 kJ of heat are evolved per gram of octane burned. For the reaction ofmethanol, CH3OH, with oxygen to produce CO2 and gaseous water, 638.6 kJ/mole methanol. On a per gram basis, from which one will more energy be produced. The density of octane is 0.7025 g/cm3 and the density of methanol is 0.7914 g/cm3. If burning octane in an automobile is 30% efficient (i.e., 30% of the energy produced is used to move the car) and burning methanol is 40% efficient, which fuel will have the larger tank to have the same mileage capability?
 
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  • #2
a good place to start is molecular weight

MW octane = 8*12+18 = 114
MW methanol = 12+3+16+1 = 32

For octane, the energy produced is 48.1 KJ/g (given)

For methanol, the energy produced is 638.6 KJ/mol (given). To convert this to KJ/g, divide by MW of methanol. Then, 638.6/32 = 19.96 KJ/g

for octane:
48.1 KJ/g * 0.7025 g/cm^3 = 33.79 KJ/cm^3 * (0.3) = 10.137 KJ/cm^3 utilized energy

for methanol:
19.96 KJ/g * 0.7914 g/cm^3 = 15.8 KJ/cm^3 * (0.4) = 6.32 KJ/cm^3 utilized energy

More energy is stored in octane per unit volume than in methanol, thus methanol will require a larger tank.
 
  • #3
I though gasolene was mostly toluene; the octane specification has to do with anti-knock properties of the engine.
 
  • #4
thanks so much! it makes so much more sense when i actually see it done out :)
 

What is gasoline?

Gasoline, also known as petrol, is a liquid fuel derived from petroleum and used to power internal combustion engines in vehicles and other machines.

How is gasoline made?

Gasoline is made through a process called fractional distillation, which separates crude oil into different components based on their boiling points. This process is then followed by refining, where additives are added to improve the fuel's performance.

What are the benefits of using gasoline?

Gasoline is easily accessible and relatively affordable compared to other forms of energy. It also has a high energy density, meaning it can produce a lot of power in a small amount, making it ideal for transportation purposes.

What are the environmental impacts of using gasoline?

The burning of gasoline produces carbon dioxide, a greenhouse gas that contributes to climate change. It also releases other pollutants such as nitrogen oxides and particulate matter, which can harm human health and the environment.

Are there alternatives to using gasoline?

Yes, there are alternative forms of energy that can be used instead of gasoline, such as electric, hybrid, and hydrogen-powered vehicles. These options are more environmentally friendly but may come with their own limitations and challenges.

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