How can burning 1 gallon of gas produce 20 lbs of pollution??

Question

I've heard this in a few different places and it just doesn't seem possible. a gallon only weighs a couple of lbs to begin with, and then most of it is burned up. How can it possibly produce 20 lbs of anything?

Answer 1

It all depends on your definition of pollutant.  The 20 lb number assumes that carbon dioxide should be counted.  Others have explained the basis.  Of the 20 lbs of CO2, only 5.5 lbs comes from the gasoline.  The rest comes from air.

Answer 2

In the carburetor of a car's engine, small amounts of fuel are sprayed into large amounts of air, and this mixture is what is combusted inside the piston cylinders. This process causes a lot of the air to turn into carbon dioxide (as well as creating other pollutants).

Answer 3

A gallon of fuel weighs about 7.5 lbs. For each gallon burned, 1 lb of carbon dioxide goes into the air.

Yuck

Answer 4

A gallon of gasoline weighs about 6 pounds. Roughly 90% of that mass is carbon or about 5.5 pounds. When that carbon is burned one atom of carbon, C, combines with one molecule of oxygen, O2, to form carbon dioxide, CO2. One molecule of CO2 weighs about 3.5 times as much as an atom of carbon, so that 5.5 pounds of carbon results in about 20 pounds of CO2.

Answer 5

Gasoline is lighter than water (which is 8 lbs. per gallon), but not by much, so lets call it 7 lbs. per gallon to be simple.  

-About 6 of the 7 pounds is carbon.

-Carbon is #5 on the periodic table, while oxygen is #8

-CO2 is 1 atom carbon (5) combined with 2 atoms of Oxygen (16) [#8 + #8] = 21, or  3 times the weight of the orriginal gallon of gasoline.    Some of the fuel isn't burnt or turns into carbon monoxide, but it still is a pollutant.