That doesn’t seem right, gas is 20-30% lighter than water and water is only 8lbs~=3600 grams.
Burn 1g of coal, to make it easy:
C + O₂ → CO₂
So burning 1g of carbon produces 3.67g of CO₂.
Burn 1g of coal, to make it easy:
Carbon has molecular mass 12g/mole (carbon has atomic weight ~12), carbon dioxide 44g/mole (12 + 2×16).So burning 1g of carbon produces 3.67g of CO₂.