The molar mass of carbon dioxide (CO2) is 44.009 g/mol.
Case matters: CO is carbon monoxide, Co is
cobalt. Brackets and hydrates are fine — try
or
.
| Element | Atoms | Atomic mass | Mass contributed | Percent |
|---|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 | 27.29% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 72.71% |
| Total | 3 | 44.009 | 100.00% |
12.011 + 31.998 = 44.009 g/mol
Grams and moles
25 g of carbon dioxide is 0.5681 mol, because 25 ÷ 44.009 = 0.5681.
These elements have no single atomic weight. Their isotopic mix varies slightly depending on where on Earth the sample came from, so the figure used here is the conventional value IUPAC publishes for when one number is needed: carbon is 12.011, and really lies between 12.0096 and 12.0116; oxygen is 15.999, and really lies between 15.99903 and 15.99977.
Carbon dioxide is 44.009 g/mol, and the striking part of the breakdown is how little of that the carbon accounts for. One carbon contributes 12.011 and the two oxygens contribute 31.998 between them, so 72.71% of the mass came out of the air rather than out of any fuel.
This is the arithmetic behind a fact that surprises people. Burning one tonne of pure carbon produces about 3.67 tonnes of carbon dioxide, a ratio that is simply 44.009 divided by 12.011. Nothing is being created: the oxygen already existed as O2 and is now bonded to the carbon. Emissions figures quoted in tonnes of CO2 have that factor built into them.
At room temperature and pressure a mole of any gas occupies roughly 24 litres, so 44 grams of this one fills about the volume of a small bucket. Frozen as dry ice, the same mole packs into around 28 millilitres.