Whither the Oxygen?

Question

Two questions really, but related.

Why doesn't anyone mention the fact that CO2 contains twice as much oxygen as it does carbon? Is it just that they don't understand chemical symbols or because there is no "fear" content in oxygen?

Those who managed that one please explain how you calculate the carbon emissions of, for example an engine. My physics master told me that you can't get out more than you put in, so how does a gallon of petrol, weighing ten pounds produce more than ten pounds of carbon when burned (and please explain how much oxygen it produces).

Answer 1

It's all a matter of understanding what petrol is and what the reaction of combustion of petrol produces:

let us say the petrol is 100% octane *(which it isn't)

2C8H18(l) + 25O2(g) --> 16CO2(g) + 18H2O(l)

thus say:

1 moles of C8H18 will emit 8 moles of CO2

1 mole C8H18 = 114 g
1 mole CO2 = 44 g

1 lb = 453.5 g

10 lb = 4535 g

10 lb C8H18 = 4535 g * mole/114g = 39.8 moles
8 mole CO2 from that would be 8*39.8 mole = 318.5 moles

= 318.5 *44g/mole = 14,028 g = 30.8 lbs

you see you get ALOT of CO2 out

Answer 2

I think I have not answered ur Q before. However.

1) CO2 , definitely contains 2 vol of Oxygen & 1 vol of Carbon.
CARBON IS NOT FATAL FOR US EITHER.In fact CO2 is not fatal or anyway near of being harmful (except that greenhouse gas fact) but certain compounds of Carbon & Oxygen eg. CO are poisonous, this is because a compound by definition do not inherit any of the properties of its constituent element. BUT MIND IT CO2 IS NOT POISONOUS.

2) ur master have provided u with the correct information, but can u cite an example where 10 lbs of petrol releases more than 10 lbs of Carbon?

Are u talking of CO2? in that case as u can see its C+ O2 ie carbon + oxygen. Then where will the wt of the combined oxygen will go? huh!?

& whoever told u that combustion of petrol produces Oxygen?!!?

Answer 3

If you go by weight, CO2 contains slightly more than twice as much oxygen as it does carbon. However, carbon dioxide acts quite differently than oxygen in the atmosphere.

If you want a fear factor, oxygen is a serious fire hazard. Because of this, oxygen is a lot more dangerous to handle than carbon dioxide. Indeed, it is very difficult to get a fire going without oxygen. It is also impossible to stay alive without it.

Also, if you count just the carbon going through the engine as fuel, the output of carbon itself is a bit less than the mass of the fuel that went in, partly because the fuel going in contains a significant amount of hydrogen as well as carbon. To a much lesser extent, some of the output is gases other than carbon dioxide and water because the fuel is incompletely burned. The car's catalytic converter is there to convert some of these other, more noxious emissions to carbon dioxide.

However, carbon dioxide doesn't just consist of carbon; the oxygen also contributes a lot to the mass of the gas that comes out. Also, for every gallon of fuel that goes in, you have also a considerable amount of oxygen that goes in as well. The extra mass of the (mostly) carbon dioxide and water that comes out is the result of the oxygen that goes into the combustion process. You can therefore have a lot more carbon dioxide - but not carbon - coming out than you had fuel going in.

Often, when computing the environmental impact of fuels, particularly when the writer wants to maximize the emotional impact, the writer doesn't count just the fuel that actually goes into the car that is included but also the fuel used in producing, refining, and distributing it, and perhaps even the fuel that goes into producing the car itself, as well as the fuel to transport the workers to and from the plant, plus...

Answer 4

Oxygen bound to carbon in the form of carbon monoxide or carbon dioxide is of no good to us. Both of these gasses are fatal to animals (us too).

Just because it has CO2 (or any other compound) has oxygen in it doesn't mean is usable as breathable oxygen or can be made to be usable. CO2 acts entirely differently than O2 in the atmosphere so it doesn't really matter that it has twice as much oxygen when it cannot be used for breathable air..
i hope this is your question answer because i canot exactly know yor question

Answer 5

i didnt really see this in anyone's answer (though i did just skim over them) but the oxygen produced by combustion is not atmospheric oxygen. carbon itself if not to be feared (after all, you are a carbon based life form.) CO2 is a carbon atom with any oxygen atom double bonded to it on either side. atmospheric oxygen is 2 oxygen atoms double bonded together. when a chemist says 'oxygen', they dont mean atmospheric oxygen, they usually mean the element oxygen. the elements carbon and oxygen have no inherent negative effects associated with them, it depends on how they are arranged in a chemical.
this being said, CO2 contains 2 elements of oxygen and 1 element of carbon, but the reason this chemical is bad is due to its greenhouse effects on the planet. the reason we concentrate on the carbon when we talk about carbon emissions is because the combustible products we are burning are hydrocarbons (petrol.) if we combust something hydrogen gas (H2), oxidizing it with atmospheric oxygen, then we get water, H2O. here there is still oxygen, but water of course is not harmful in anyway, unlike CO2.
as for your second question, i believe it has already been sufficiently shown that the additional weight comes from the atmospheric oxygen that is added to the weight of carbon when combusted.

Answer 6

Oxygen bound to carbon in the form of carbon monoxide or carbon dioxide is of no good to us. Both of these gasses are fatal to animals (us too).

Just because it has CO2 (or any other compound) has oxygen in it doesn't mean is usable as breathable oxygen or can be made to be usable. CO2 acts entirely differently than O2 in the atmosphere so it doesn't really matter that it has twice as much oxygen when it cannot be used for breathable air..

Answer 7

10 lbs of petrol can't produce more than 10 lbs of carbon when it's also producing CO2 and water vapour along with other combustion products.
The oxygen produced is no longer oxygen as such as it has combined with hydrogen from the petrol molecules to form water vapour.
There are calculations that can be performed to find the amount of each product formed by the combustion of hydrocarbons.

Answer 8

CO2 may contain twice as many oxygen atoms as carbon atoms but that doesn't mean that they will share any properties relevant to either. And when a hydrocarbon burns, it's combined with oxygen (and some nitrogen). So when you burn ten lbs of gas you not burning ten lbs total. You have to acount for the mass of the oxygen and nitrogen added to the gasoline when calculating the mass of the ommisions.

Answer 9

Why would anyone fear carbon?

Okay, take your engine fuel. For simplicity, assume its one chemical like octane. thats 8 carbons long and has a mass of ~114g/mol. Soooo... you burn it. You make 8 CO2's each of which weighs 44g/mol. So you have produced 350g/mol of CO2. You have the same amount of carbon out as put in only it measures about 3 times the mass. So ten pounds of Octane in, means 30 pounds of CO2 out.
about 85% of the fuel is carbon, only about 31% of the exhaust is carbon.

Hope that helps.