The molar mass of carbon monoxide (CO) is 28.010 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 | 42.88% |
| Oxygen (O) | 1 | 15.999 | 15.999 | 57.12% |
| Total | 2 | 28.010 | 100.00% |
12.011 + 15.999 = 28.010 g/mol
Grams and moles
25 g of carbon monoxide is 0.8925 mol, because 25 ÷ 28.010 = 0.8925.
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.
This gas weighs 28.010 g/mol. Nitrogen gas weighs 28.014. Those two figures sit four parts in ten thousand apart, and the near-identity is a practical problem rather than a curiosity.
Both carry fourteen electrons, and their boiling points, densities and viscosities track each other closely. A gas chromatograph will not separate them on an ordinary column, and a low-resolution mass spectrometer sees one peak at mass 28 for both. Distinguishing them takes chemistry, such as oxidising the monoxide to carbon dioxide and measuring that instead, or a high-resolution instrument.
It is also within a whisker of the density of air itself, so it neither rises nor settles. It disperses evenly through a room, which is why detectors work at any mounting height and why the gas is so dangerous: it is odourless, colourless, and gives no positional warning.
Its toxicity comes from binding haemoglobin some 200 times more tightly than oxygen does.