Moles are the hinge between grams and particles
You can weigh grams and you can count particles, but the two only connect through moles. Molar mass takes you from grams to moles; Avogadro number takes you from moles to particles. Always route through the middle.
Common molar masses
Molar mass is just the sum of the atomic masses in the formula, read off the periodic table (H ≈ 1, C ≈ 12, O ≈ 16). These are the values the converter needs.
| Substance | Formula | Molar mass (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Table salt | NaCl | 58.443 |
| Carbon dioxide | CO₂ | 44.009 |
| Sucrose (sugar) | C₁₂H₂₂O₁₁ | 342.30 |
| Oxygen gas | O₂ | 31.998 |
| Ethanol | C₂H₅OH | 46.068 |
Use the molecular formula, not the atom: oxygen gas is O₂ at 32 g/mol, not O at 16 g/mol.
The three conversions, and where they break
- Grams → moles. Divide by molar mass. Grams → particles is the same step then × 6.022×1023.
- Moles → mass. Multiply by molar mass. One mole of water is 18 g, not 1 g — keep the units attached.
- Diatomic gases. Oxygen, nitrogen, hydrogen, chlorine travel as pairs (O₂, N₂). Doubling the atomic mass is the single most common error.
Common questions
How do I convert grams to moles?
Divide the mass in grams by the molar mass in grams per mole. For example, 36 g of water divided by 18.015 g/mol is about 2 moles.
How many particles are in one mole?
Exactly 6.02214076 times 10 to the 23rd power. That figure is Avogadro number, and since 2019 it is a fixed defined value rather than a measurement.
Why do I have to go through moles to reach particles?
Molar mass links grams to moles and Avogadro number links moles to particles, so moles are the hinge in the middle. Converting grams straight to particles is where most mistakes happen.
