Yesterday I was in a museum (Museon, Den Haag) where was said that 1 liter gasoline produces more then 2 kilogram CO2. Please explain this.
In: Chemistry
Gasoline is about 750 g/L. So 1 L of gas weighs about 750 grams, and most of that mass is carbon atoms. When you burn gasoline, it mostly makes CO2 and water vapour. CO2 is heavier than carbon atoms because it has two oxygen atoms (that it got from the fresh air required for the combustion reaction.) So yeah, the math checks out. 1L of gasoline actually produces more like 2.3 kg of CO2.
CO2 consist from C (carbon) and O2 (oxygen). Fuel needs air in able to combust. The carbon is from the fuel, but the O2 is taken from air. So the weight of CO2 consists from combination of the fuel and incoming air.
The gasoline molecules have hydrogen atoms, and when it burns it *trades* those for oxygen atoms, which are heavier
CO2 contains oxygen in addition to carbon. The carbon comes from the gasoline and the oxygen comes from the air. Most of the mass of CO2 was already in the atmosphere as O2.
Would you be confused if you were reading a recipe where it said you need 250grams of flour to make 500 grams of cookies? There’s more to the recipe.
The carbon in gasoline reacts with oxygen (O2 weighs ~2.6x as much as the carbon) to make carbon dioxide.
So for every kg of carbon in your fuel, which your fuel will be ~85% carbon by weight, it will make ~2.6kg of carbon.
Since gasoline is about 750 g/L, that means your final amount of CO2 released will be somewhere around
750g/L * 0.85 * (1 + 2.6) = ~2295g of CO2 per Liter of gasoline burned.
In order for gasoline to produce CO2, it has to be burned, which is a chemical reaction, and gasoline is not the only ingredient in that chemical reaction.
It also takes oxygen molecules (O2) from the air, as all combustion reactions do. So the end products of that reaction are heavier than the gasoline that went in because they also include the weight from all those oxygen molecules.
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