The molar mass of nitrogen gas (N2) is 28.014 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 |
|---|---|---|---|---|
| Nitrogen (N) | 2 | 14.007 | 28.014 | 100.00% |
| Total | 2 | 28.014 | 100.00% |
28.014 = 28.014 g/mol
Grams and moles
25 g of nitrogen gas is 0.8924 mol, because 25 ÷ 28.014 = 0.8924.
This element has 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: nitrogen is 14.007, and really lies between 14.00643 and 14.00728.
Nitrogen gas is 28.014 g/mol and makes up 78% of the atmosphere by volume. Like oxygen it is diatomic, so the relevant mass is that of N2 rather than the 14.007 of a single atom.
The number is worth committing to memory for an unexpected reason: carbon monoxide is 28.010 g/mol. Four parts in ten thousand separate the two, which no ordinary balance and no simple mass spectrometer setting will resolve. They also have the same number of electrons and very similar physical properties. Analysers that need to distinguish them rely on chemistry or on high-resolution mass spectrometry rather than on weight, and the near-collision is a standard headache in combustion gas analysis.
The triple bond holding N2 together is one of the strongest in chemistry, which is why atmospheric nitrogen is almost inert and why fixing it into ammonia takes the pressure, temperature and catalyst of the Haber process.