Molar Mass of Carbon Dioxide

Carbon dioxide is 44.009 g/mol against carbon's 12.011, a ratio of 3.664. That single number underlies every emissions inventory on earth: burn a tonne of pure carbon and you put 3.664 tonnes of CO₂ into the atmosphere, because each carbon atom drags two oxygen atoms out of the air with it. A litre of gasoline, roughly 0.75 kg at about 86 % carbon by mass, yields close to 2.3 kg of CO₂.

In water chemistry the same molar mass converts dissolved CO₂ to carbonic acid concentration, which is what fixes the pH of rainwater at about 5.6 before any pollution is added: atmospheric CO₂ alone is enough to make natural rain mildly acidic. Being heavier than air at 1.98 g/L, CO₂ also pools in cellars, silos and ship holds, and a molar mass calculation is the first step in sizing the ventilation that keeps those spaces survivable.