Molar MassMolar mass of sodium oxide (Na2O)
The molar mass of sodium oxide, Na2O, is 61.98 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 61.98 grams.
About sodium oxide
Sodium oxide is a white solid that reacts with water to give sodium hydroxide. Glass compositions are often quoted as percentages of it.
The working
The formula Na2O has 2 sodium atoms and 1 oxygen atom, 3 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Sodium (Na) | 2 | 22.990 | 45.980 | 74.19% |
| Oxygen (O) | 1 | 15.999 | 15.999 | 25.81% |
2 × 22.990 + 15.999 = 61.979 g/mol
With the rounded atomic masses used in many school books (Na = 23, O = 16) the answer is 62 g/mol. The difference from 61.98 is too small to matter in most school sums.
Percentage composition
By mass, Na2O is 74.19% sodium and 25.81% oxygen. The largest share comes from sodium. In a 100 g sample there are 74.2 g of sodium and 25.8 g of oxygen.
Worked examples
Grams to moles. How many moles are in 100 g of Na2O? Divide the mass by the molar mass: 100 ÷ 61.98 = 1.613 mol.
Moles to grams. What is the mass of 2 mol of Na2O? Multiply: 2 × 61.98 = 124 g.
Counting particles. 100 g contains 1.613 mol × 6.022 × 1023 = 9.716 × 1023 formula units.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 6.198 g |
| 0.5 mol | 30.99 g |
| 1 mol | 61.98 g |
| 2 mol | 124 g |
| 5 mol | 309.9 g |
| Mass | Moles |
|---|---|
| 1 g | 0.01613 mol |
| 10 g | 0.1613 mol |
| 100 g | 1.613 mol |
| 1 kg | 16.13 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of Na2O?
The molar mass of sodium oxide (Na2O) is 61.98 g/mol, or 61.979 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of Na2O?
100 ÷ 61.98 = 1.613 mol.
What is the mass of one formula unit of Na2O?
Divide the molar mass by the Avogadro constant: 61.98 ÷ 6.022 × 1023 = 1.029 × 10-22 g.
What is the percentage of sodium in Na2O?
Sodium makes up 74.19% of the mass of Na2O: 2 × 22.990 ÷ 61.979 × 100.
Which values? This site uses the abridged standard atomic weights published by IUPAC (CIAAW), read on 12 November 2026. Your textbook or question paper may round them differently, for example H = 1 and O = 16, so its answer can differ slightly. In an exam, use the values the paper gives.