Moles to grams for sulfur dioxide is a multiplication by 64.058 g/mol. A mole weighs 64.058 g, 100 mmol weighs 6.4058 g, 10 mmol weighs 0.64058 g and a millimole is 64.058 mg. Those four figures cover most of what gets weighed out in practice, and the table below extends them from a micromole up to ten moles.
The figure comes from the formula. Sulfur dioxide is 32.06 (S) + 2 × 15.999 (O), which is 64.058 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Sulfur makes up the largest share of the mass: 1 of the 3 atoms in a formula unit is sulfur, and they account for 32.06 g of the 64.058 g, or 50.05% by mass. The derivation table below breaks the whole molecule down element by element.
Two habits make the weighed mass match the calculation. Weigh into a container you have tared rather than onto paper, because what stays behind on paper is a real loss — on a 100 mg weighing it is easily a percent. And when the target is under about 20 mg, weigh ten times that and dilute, since the absolute error of the balance does not shrink with the sample.
The wine preservative and the gas of coal smoke, measured in parts per million in air and in mg per litre in wine. At 64.058 g/mol it is the heaviest of the 11 gases and small molecules covered here, and that ranking matters more than it looks: butane has a molar mass of 58.124 g/mol, so a gram of it contains 10.2% more formula units than a gram of sulfur dioxide. Weigh by mass and you are not weighing equal amounts of substance.
Because this is a gas, volume is often the easier measure. One mole of any ideal gas occupies 22.414 L at 0 °C and 1 atm and 24.4655 L at 25 °C, so 64.058 g of sulfur dioxide — one mole — fills about 24.47 litres at room temperature. Real gases depart from that by a percent or so, more near their boiling point, but for ordinary work the molar volume is the quickest route from grams to litres.
The formula
n- The amount of sulfur dioxide you need, in moles
64.058- The molar mass of sulfur dioxide in g/mol, derived from its formula
m- The mass to weigh out, in grams
How it works, step by step
- Enter the amount you need, in moles.
- It is multiplied by 64.058 g/mol.
- The result is the mass to weigh out, also given in milligrams.
- Weigh into a tared container; anything left in the boat is a real loss from the amount you calculated.
Worked examples
5 mmol of sulfur dioxide in grams
5 mmol × 64.058 g/mol = 0.32029 g, which is 320.29 mg. Doubling the amount doubles the mass to 0.64058 g, because the relationship is a plain proportion once the molar mass is fixed.
250 mmol of sulfur dioxide in grams
250 mmol × 64.058 g/mol = 16.0145 g, which is 16,014.5 mg. Doubling the amount doubles the mass to 32.029 g, because the relationship is a plain proportion once the molar mass is fixed.
2 mol of sulfur dioxide in grams
2 mol × 64.058 g/mol = 128.116 g, which is 128,116 mg. Doubling the amount doubles the mass to 256.232 g, because the relationship is a plain proportion once the molar mass is fixed.
How to read your score
Frequently asked questions
What is the molar mass of sulfur dioxide (SO2)?
It is 64.058 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 32.06 (S) + 2 × 15.999 (O). One mole of sulfur dioxide therefore weighs 64.058 g, and a gram of it is 15.611 mmol.
What percentage of sulfur dioxide is sulfur?
50.05% by mass. Each formula unit contains 1 sulfur atom contributing 32.06 g of the 64.058 g total, so 100 g of sulfur dioxide contains 50.05 g of sulfur and a kilogram contains 500.48 g of it.
How many grams is one mole of sulfur dioxide?
64.058 g, by definition of the molar mass. Two moles is 128.116 g and half a mole is 32.029 g.
How many grams is 0.1 mol, and how many milligrams is 1 mmol?
0.1 mol of sulfur dioxide is 6.4058 g. One millimole is 64.058 mg and one micromole is 64.058 µg, which is the range most bench work sits in.
How do I weigh out an amount too small for my balance?
Weigh a larger mass and dilute it. To get 0.6406 mg of sulfur dioxide, weigh 6.406 mg into 100 mL, then take 10 mL of that: the absolute error of the balance stays the same while the amount delivered falls by a factor of ten.
Should I use the hydrate or the anhydrous molar mass?
This page is the anhydrous form, SO2, at 64.058 g/mol. If your jar is the other form the molar mass differs and so will every mass you weigh, so check the label before using the figure. Salts that are sold as hydrates weigh more per mole because the water is part of the crystal.
Moles to grams reference for sulfur dioxide
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Sulfur (S) | 1 | 32.06 | 32.06 | 50.05% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 49.95% |
| Total — one mole of sulfur dioxide | 64.058 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 64.058 g/mol.
| Wanted | Weigh (g) | Weigh (mg) | With 2% over (g) |
|---|---|---|---|
| 1 µmol | 0.000064 | 0.064058 | 0.000065 |
| 10 µmol | 0.00064058 | 0.64058 | 0.000653392 |
| 100 µmol | 0.0064058 | 6.4058 | 0.00653392 |
| 1 mmol | 0.064058 | 64.058 | 0.0653392 |
| 10 mmol | 0.64058 | 640.58 | 0.653392 |
| 50 mmol | 3.2029 | 3202.9 | 3.26696 |
| 100 mmol | 6.4058 | 6405.8 | 6.53392 |
| 250 mmol | 16.0145 | 16,014.5 | 16.3348 |
| 500 mmol | 32.029 | 32,029 | 32.6696 |
| 750 mmol | 48.0435 | 48,043.5 | 49.0044 |
| 1 mol | 64.058 | 64,058 | 65.3392 |
| 2 mol | 128.116 | 128,116 | 130.678 |
| 5 mol | 320.29 | 320,290 | 326.696 |
| 10 mol | 640.58 | 640,580 | 653.392 |
Weigh is the amount multiplied by 64.058 g/mol. The last column carries a 2% allowance, which is what you take when some of the solid will be left in the weighing boat.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Nitrogen | N2 | 28.014 | 35.696 |
| Oxygen | O2 | 31.998 | 31.252 |
| Hydrogen peroxide | H2O2 | 34.014 | 29.4 |
| Carbon dioxide | CO2 | 44.009 | 22.723 |
| Propane | C3H8 | 44.097 | 22.677 |
| Butane | C4H10 | 58.124 | 17.205 |
| Sulfur dioxide (this page) | SO2 | 64.058 | 15.611 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.