Molar MassMolar mass of sodium sulphate (Na2SO4)
The molar mass of sodium sulphate, Na2SO4, is 142.04 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 142.04 grams.
142.04 g/mol
2 × 22.990 + 32.06 + 4 × 15.999 = 142.036 · 7 atoms in the formula · also called sodium sulfate
About sodium sulphate
Sodium sulphate is a white salt used in making detergents, glass and paper. The decahydrate is called Glauber's salt. In the anhydrous form it is used to dry organic solutions.
Other names: sodium sulfate.
The working
The formula Na2SO4 has 2 sodium atoms, 1 sulphur atom and 4 oxygen atoms, 7 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 | 32.37% |
| Sulphur (S) | 1 | 32.06 | 32.060 | 22.57% |
| Oxygen (O) | 4 | 15.999 | 63.996 | 45.06% |
2 × 22.990 + 32.06 + 4 × 15.999 = 142.036 g/mol
With the rounded atomic masses used in many school books (Na = 23, S = 32, O = 16) the answer is 142 g/mol. The difference from 142.04 is too small to matter in most school sums.
Percentage composition
By mass, Na2SO4 is 32.37% sodium, 22.57% sulphur and 45.06% oxygen. The largest share comes from oxygen. In a 100 g sample there are 32.4 g of sodium, 22.6 g of sulphur and 45.1 g of oxygen.
Worked examples
Grams to moles. How many moles are in 50 g of Na2SO4? Divide the mass by the molar mass: 50 ÷ 142.04 = 0.352 mol.
Moles to grams. What is the mass of 0.4 mol of Na2SO4? Multiply: 0.4 × 142.04 = 56.81 g.
Counting particles. 50 g contains 0.352 mol × 6.022 × 1023 = 2.120 × 1023 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 142.04 = 14.2 g of Na2SO4 in each litre. For 250 mL, weigh 3.551 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 14.2 g |
| 0.5 mol | 71.02 g |
| 1 mol | 142 g |
| 2 mol | 284.1 g |
| 5 mol | 710.2 g |
| Mass | Moles |
|---|---|
| 1 g | 0.00704 mol |
| 10 g | 0.0704 mol |
| 100 g | 0.704 mol |
| 1 kg | 7.04 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of Na2SO4?
The molar mass of sodium sulphate (Na2SO4) is 142.04 g/mol, or 142.036 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of Na2SO4?
100 ÷ 142.04 = 0.704 mol.
What is the mass of one formula unit of Na2SO4?
Divide the molar mass by the Avogadro constant: 142.04 ÷ 6.022 × 1023 = 2.359 × 10-22 g.
What is the percentage of oxygen in Na2SO4?
Oxygen makes up 45.06% of the mass of Na2SO4: 4 × 15.999 ÷ 142.036 × 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.