Molar MassMolar mass of sodium nitrate (NaNO3)
The molar mass of sodium nitrate, NaNO3, is 84.99 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 84.99 grams.
84.99 g/mol
22.990 + 14.007 + 3 × 15.999 = 84.994 · 5 atoms in the formula · also called Chile saltpetre
About sodium nitrate
Sodium nitrate is found in large natural deposits in Chile. It is used as a fertiliser and in making nitric acid and glass. On heating it gives sodium nitrite and oxygen.
Other names: Chile saltpetre.
The working
The formula NaNO3 has 1 sodium atom, 1 nitrogen atom and 3 oxygen atoms, 5 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) | 1 | 22.990 | 22.990 | 27.05% |
| Nitrogen (N) | 1 | 14.007 | 14.007 | 16.48% |
| Oxygen (O) | 3 | 15.999 | 47.997 | 56.47% |
22.990 + 14.007 + 3 × 15.999 = 84.994 g/mol
With the rounded atomic masses used in many school books (Na = 23, N = 14, O = 16) the answer is 85 g/mol. The difference from 84.99 is too small to matter in most school sums.
Percentage composition
By mass, NaNO3 is 27.05% sodium, 16.48% nitrogen and 56.47% oxygen. The largest share comes from oxygen. In a 100 g sample there are 27.0 g of sodium, 16.5 g of nitrogen and 56.5 g of oxygen.
Worked examples
Grams to moles. How many moles are in 250 g of NaNO3? Divide the mass by the molar mass: 250 ÷ 84.99 = 2.941 mol.
Moles to grams. What is the mass of 0.2 mol of NaNO3? Multiply: 0.2 × 84.99 = 17 g.
Counting particles. 250 g contains 2.941 mol × 6.022 × 1023 = 1.771 × 1024 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 84.99 = 8.499 g of NaNO3 in each litre. For 250 mL, weigh 2.125 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 8.499 g |
| 0.5 mol | 42.5 g |
| 1 mol | 84.99 g |
| 2 mol | 170 g |
| 5 mol | 425 g |
| Mass | Moles |
|---|---|
| 1 g | 0.01177 mol |
| 10 g | 0.1177 mol |
| 100 g | 1.177 mol |
| 1 kg | 11.77 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of NaNO3?
The molar mass of sodium nitrate (NaNO3) is 84.99 g/mol, or 84.994 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of NaNO3?
100 ÷ 84.99 = 1.177 mol.
What is the mass of one formula unit of NaNO3?
Divide the molar mass by the Avogadro constant: 84.99 ÷ 6.022 × 1023 = 1.411 × 10-22 g.
What is the percentage of oxygen in NaNO3?
Oxygen makes up 56.47% of the mass of NaNO3: 3 × 15.999 ÷ 84.994 × 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.