Molar mass of O2 (Oxygen)
The molar mass of O2 is 32.00 g/mol.
The gas that relights a glowing splint.
Step-by-step calculation
Add up the atomic masses of every atom in the formula:
2 × 15.999 = 32.00 g/mol
| Element | Atoms | Atomic mass (u) | Subtotal (g/mol) | % by mass |
|---|---|---|---|---|
| Oxygen (O) | 2 | 15.999 | 31.998 | 100.00% |
| Molar mass of O2 | 32.00 g/mol | |||
Moles to grams for O2
Multiply the number of moles by 32.00 g/mol to get the mass, and divide a mass by 32.00 g/mol to get the moles.
| Amount (mol) | Mass (g) | Mass (g) | Amount (mol) |
|---|---|---|---|
| 0.1 mol | 3.20 g | 1 g | 0.0313 mol |
| 0.25 mol | 8.00 g | 5 g | 0.1563 mol |
| 0.5 mol | 16.00 g | 10 g | 0.3125 mol |
| 1 mol | 32.00 g | 50 g | 1.5626 mol |
| 2 mol | 64.00 g | 100 g | 3.1252 mol |
| 5 mol | 159.99 g | 500 g | 15.6260 mol |
Experiments that use oxygen
🐘 Elephant's toothpaste
Iodide-catalysed decomposition of 30% hydrogen peroxide produces a towering, steaming foam.
🔥 Preparing oxygen
Heat potassium permanganate, pipe the gas into a gas jar and confirm with a glowing splint.
⚡ Electrolysis of water
Split water in a Hofmann voltameter: twice as much hydrogen as oxygen.
🎆 Burning in oxygen
Magnesium, sulfur and iron burn far more fiercely in pure oxygen.
Frequently asked questions
What is the molar mass of O2?
The molar mass of O₂ (oxygen) is 32.00 g/mol, so one mole of oxygen weighs 32.00 grams.
How do you calculate the molar mass of O2?
Multiply each element’s atomic mass by the number of atoms in the formula and add the results: 2 × 15.999 = 32.00 g/mol.
What percentage of O2 is oxygen?
Oxygen makes up 100.00% of the mass of O₂.
How many grams are in one mole of O2?
One mole of O₂ has a mass of 32.00 grams, and contains 6.022 × 10²³ formula units.