The molar mass of sulfur dioxide (SO2) is 64.058 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 |
|---|---|---|---|---|
| Oxygen (O) | 2 | 15.999 | 31.998 | 49.95% |
| Sulfur (S) | 1 | 32.06 | 32.060 | 50.05% |
| Total | 3 | 64.058 | 100.00% |
31.998 + 32.060 = 64.058 g/mol
Grams and moles
25 g of sulfur dioxide is 0.3903 mol, because 25 ÷ 64.058 = 0.3903.
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: oxygen is 15.999, and really lies between 15.99903 and 15.99977; sulfur is 32.06, and really lies between 32.059 and 32.076.
Sulfur dioxide is 64.058 g/mol and it is almost exactly half sulfur by mass: 50.05% sulfur against 49.95% oxygen. Few compounds divide so evenly, and the reason is coincidence rather than chemistry, since sulfur at 32.06 happens to weigh almost the same as two oxygens at 31.998.
It is more than twice as dense as air, so it pools in low ground, which matters around volcanic vents and in fumigated spaces.
The compound is the main precursor of acid rain. Burning sulfur-bearing coal releases it, atmospheric oxidation converts it to sulfur trioxide at 80.057 g/mol, and that dissolves in water to give sulfuric acid. Following the masses through that sequence shows why flue gas desulfurisation is worth the expense: every tonne of sulfur burned eventually yields about three tonnes of sulfuric acid.
In small quantities it is a food preservative, which is why dried fruit and wine labels carry a sulfite declaration.