The molar mass of ammonium nitrate (NH4NO3) is 80.043 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 |
|---|---|---|---|---|
| Hydrogen (H) | 4 | 1.0080 | 4.032 | 5.04% |
| Nitrogen (N) | 2 | 14.007 | 28.014 | 35.00% |
| Oxygen (O) | 3 | 15.999 | 47.997 | 59.96% |
| Total | 9 | 80.043 | 100.00% |
4.032 + 28.014 + 47.997 = 80.043 g/mol
Grams and moles
25 g of ammonium nitrate is 0.3123 mol, because 25 ÷ 80.043 = 0.3123.
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: hydrogen is 1.0080, and really lies between 1.00784 and 1.00811; nitrogen is 14.007, and really lies between 14.00643 and 14.00728; oxygen is 15.999, and really lies between 15.99903 and 15.99977.
Ammonium nitrate is 80.043 g/mol, and the striking feature of the breakdown is that nitrogen appears twice in different chemical roles. One nitrogen sits in the ammonium cation, the other in the nitrate anion, and together they make up exactly 35.00% of the mass.
That figure is why the compound dominates fertiliser. It is sold as 34-0-0, meaning roughly 34% nitrogen with no phosphorus or potassium, and the small shortfall against 35.00% is the anti-caking coating rather than a chemistry error. No other common solid delivers nitrogen so densely.
The same property makes it hazardous. The molecule already carries its own oxygen, so it does not need air to decompose, and under heat and confinement that decomposition can become detonation. The Beirut and Texas City disasters were both stored ammonium nitrate.
Dissolving it absorbs heat strongly, which is the basis of the instant cold pack.