Burning one gallon of gasoline produces 20 pounds of Carbon Dioxide or CO₂.
It seems paradoxical that a gallon of gasoline weighing 6.25 pounds (2.83 kg) can produce 20 pounds of anything but let’s investigate that.

Gasoline (oroctane) has the chemical formula C₈H₁₈or 8 parts carbon and 18 parts hydrogen.
Looking up the atomic mass – carbon is 12 and hydrogen is 1.
So, the molecular mass of gasoline is 12 × 8 plus 18 × 1 which equals 114.

Okay getting technical here, amoleof gasoline weighs 114 grams and a gallon of gas weighs 2,834 grams.
Therefore a gallon of gas contains (2,834 ÷ 114) 24.86 moles.

The chemical equation for the combustion of gasoline is:

2 C₈H₁₈+ 25 O₂ → 16 CO₂+ 18 H₂O

Which can be rewritten as:

C₈H₁₈+ 12½ O₂ → 8 CO₂+ 9 H₂O

This means thatburning 1 mole of gasoline produces 8 moles of carbon dioxide.
Therefore, a gallon of gasoline (24.86 moles) produces 198.91 moles (24.86 × 8 = 198.91) of carbon dioxide.

And what is the mass of 198.91 moles of carbon dioxide? (Basically, what does it weigh?)
First we have to determine the molecular mass of carbon dioxide.
Atomic mass of O₂= 32 plus the atomic mass of carbon,12, equals 44.
So, the mass of 198.91 moles of carbon dioxide = 198.91 × 44 = 8,752 grams = 8.752 kilograms, which converts to 19.3 pounds.

We can therefore say that burning 100 gallons of gasoline produces onetonof carbon dioxide!