Molar MassMolar mass of ammonium sulphate ((NH4)2SO4)
The molar mass of ammonium sulphate, (NH4)2SO4, is 132.13 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 132.13 grams.
132.13 g/mol
2 × 14.007 + 8 × 1.0080 + 32.06 + 4 × 15.999 = 132.134 · 15 atoms in the formula · also called ammonium sulfate
About ammonium sulphate
Ammonium sulphate is a common nitrogen fertiliser. The bracket holds two ammonium ions, so the formula has two nitrogen and eight hydrogen atoms. Working out its nitrogen percentage is a classic school question.
Other names: ammonium sulfate.
The working
The formula (NH4)2SO4 has 2 nitrogen atoms, 8 hydrogen atoms, 1 sulphur atom and 4 oxygen atoms, 15 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Nitrogen (N) | 2 | 14.007 | 28.014 | 21.20% |
| Hydrogen (H) | 8 | 1.0080 | 8.064 | 6.10% |
| Sulphur (S) | 1 | 32.06 | 32.060 | 24.26% |
| Oxygen (O) | 4 | 15.999 | 63.996 | 48.43% |
2 × 14.007 + 8 × 1.0080 + 32.06 + 4 × 15.999 = 132.134 g/mol
With the rounded atomic masses used in many school books (N = 14, H = 1, S = 32, O = 16) the answer is 132 g/mol. The difference from 132.13 is too small to matter in most school sums.
Percentage composition
By mass, (NH4)2SO4 is 21.20% nitrogen, 6.10% hydrogen, 24.26% sulphur and 48.43% oxygen. The largest share comes from oxygen. In a 100 g sample there are 21.2 g of nitrogen, 6.1 g of hydrogen, 24.3 g of sulphur and 48.4 g of oxygen.
Notice that hydrogen has more atoms in the formula (8) than oxygen (4), yet gives a smaller share of the mass. Percentage by mass depends on how heavy each atom is, not only on how many there are.
Worked examples
Grams to moles. How many moles are in 40 g of (NH4)2SO4? Divide the mass by the molar mass: 40 ÷ 132.13 = 0.3027 mol.
Moles to grams. What is the mass of 3 mol of (NH4)2SO4? Multiply: 3 × 132.13 = 396.4 g.
Counting particles. 40 g contains 0.3027 mol × 6.022 × 1023 = 1.823 × 1023 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 132.13 = 13.21 g of (NH4)2SO4 in each litre. For 250 mL, weigh 3.303 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 13.21 g |
| 0.5 mol | 66.07 g |
| 1 mol | 132.1 g |
| 2 mol | 264.3 g |
| 5 mol | 660.7 g |
| Mass | Moles |
|---|---|
| 1 g | 0.007568 mol |
| 10 g | 0.07568 mol |
| 100 g | 0.7568 mol |
| 1 kg | 7.568 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of (NH4)2SO4?
The molar mass of ammonium sulphate ((NH4)2SO4) is 132.13 g/mol, or 132.134 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of (NH4)2SO4?
100 ÷ 132.13 = 0.7568 mol.
What is the mass of one formula unit of (NH4)2SO4?
Divide the molar mass by the Avogadro constant: 132.13 ÷ 6.022 × 1023 = 2.194 × 10-22 g.
What is the percentage of oxygen in (NH4)2SO4?
Oxygen makes up 48.43% of the mass of (NH4)2SO4: 4 × 15.999 ÷ 132.134 × 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.