Molar MassMolar mass of zinc sulphate (ZnSO4)
The molar mass of zinc sulphate, ZnSO4, is 161.44 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 161.44 grams.
161.44 g/mol
65.38 + 32.06 + 4 × 15.999 = 161.436 · 6 atoms in the formula · also called zinc sulfate
About zinc sulphate
Zinc sulphate is a colourless salt used in zinc supplements, in fertilisers for zinc-poor soils and in electroplating. The crystals sold are usually the heptahydrate, called white vitriol.
Other names: zinc sulfate.
The working
The formula ZnSO4 has 1 zinc atom, 1 sulphur atom and 4 oxygen atoms, 6 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Zinc (Zn) | 1 | 65.38 | 65.380 | 40.50% |
| Sulphur (S) | 1 | 32.06 | 32.060 | 19.86% |
| Oxygen (O) | 4 | 15.999 | 63.996 | 39.64% |
65.38 + 32.06 + 4 × 15.999 = 161.436 g/mol
With the rounded atomic masses used in many school books (Zn = 65, S = 32, O = 16) the answer is 161 g/mol. The difference from 161.44 is too small to matter in most school sums.
Percentage composition
By mass, ZnSO4 is 40.50% zinc, 19.86% sulphur and 39.64% oxygen. The largest share comes from zinc. In a 100 g sample there are 40.5 g of zinc, 19.9 g of sulphur and 39.6 g of oxygen.
Worked examples
Grams to moles. How many moles are in 100 g of ZnSO4? Divide the mass by the molar mass: 100 ÷ 161.44 = 0.6194 mol.
Moles to grams. What is the mass of 2 mol of ZnSO4? Multiply: 2 × 161.44 = 322.9 g.
Counting particles. 100 g contains 0.6194 mol × 6.022 × 1023 = 3.730 × 1023 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 161.44 = 16.14 g of ZnSO4 in each litre. For 250 mL, weigh 4.036 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 16.14 g |
| 0.5 mol | 80.72 g |
| 1 mol | 161.4 g |
| 2 mol | 322.9 g |
| 5 mol | 807.2 g |
| Mass | Moles |
|---|---|
| 1 g | 0.006194 mol |
| 10 g | 0.06194 mol |
| 100 g | 0.6194 mol |
| 1 kg | 6.194 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of ZnSO4?
The molar mass of zinc sulphate (ZnSO4) is 161.44 g/mol, or 161.436 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of ZnSO4?
100 ÷ 161.44 = 0.6194 mol.
What is the mass of one formula unit of ZnSO4?
Divide the molar mass by the Avogadro constant: 161.44 ÷ 6.022 × 1023 = 2.681 × 10-22 g.
What is the percentage of zinc in ZnSO4?
Zinc makes up 40.50% of the mass of ZnSO4: 1 × 65.38 ÷ 161.436 × 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.