Molar MassMolar mass of ammonium hydroxide (NH4OH)
The molar mass of ammonium hydroxide, NH4OH, is 35.05 g/mol. One mole of it, which is 6.022 × 1023 molecules, has a mass of 35.05 grams.
35.05 g/mol
14.007 + 5 × 1.0080 + 15.999 = 35.046 · 7 atoms in the formula · also called ammonia solution, liquor ammonia
About ammonium hydroxide
Ammonium hydroxide is the name traditionally given to ammonia dissolved in water. The formula NH4OH is a convenient way of writing the solution; it has the same atoms as one ammonia molecule plus one water molecule.
Other names: ammonia solution, liquor ammonia.
The working
The formula NH4OH has 1 nitrogen atom, 5 hydrogen atoms and 1 oxygen atom, 7 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) | 1 | 14.007 | 14.007 | 39.97% |
| Hydrogen (H) | 5 | 1.0080 | 5.040 | 14.38% |
| Oxygen (O) | 1 | 15.999 | 15.999 | 45.65% |
14.007 + 5 × 1.0080 + 15.999 = 35.046 g/mol
With the rounded atomic masses used in many school books (N = 14, H = 1, O = 16) the answer is 35 g/mol. The difference from 35.05 is too small to matter in most school sums.
Percentage composition
By mass, NH4OH is 39.97% nitrogen, 14.38% hydrogen and 45.65% oxygen. The largest share comes from oxygen. In a 100 g sample there are 40.0 g of nitrogen, 14.4 g of hydrogen and 45.7 g of oxygen.
Notice that hydrogen has more atoms in the formula (5) than oxygen (1), 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 50 g of NH4OH? Divide the mass by the molar mass: 50 ÷ 35.05 = 1.427 mol.
Moles to grams. What is the mass of 0.4 mol of NH4OH? Multiply: 0.4 × 35.05 = 14.02 g.
Counting particles. 50 g contains 1.427 mol × 6.022 × 1023 = 8.592 × 1023 molecules, and 6.014 × 1024 atoms in all.
Making a solution. A 0.1 mol/L solution contains 0.1 × 35.05 = 3.505 g of NH4OH in each litre. For 250 mL, weigh 0.8761 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 3.505 g |
| 0.5 mol | 17.52 g |
| 1 mol | 35.05 g |
| 2 mol | 70.09 g |
| 5 mol | 175.2 g |
| Mass | Moles |
|---|---|
| 1 g | 0.02853 mol |
| 10 g | 0.2853 mol |
| 100 g | 2.853 mol |
| 1 kg | 28.53 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of NH4OH?
The molar mass of ammonium hydroxide (NH4OH) is 35.05 g/mol, or 35.046 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of NH4OH?
100 ÷ 35.05 = 2.853 mol.
What is the mass of one molecule of NH4OH?
Divide the molar mass by the Avogadro constant: 35.05 ÷ 6.022 × 1023 = 5.820 × 10-23 g.
What is the percentage of oxygen in NH4OH?
Oxygen makes up 45.65% of the mass of NH4OH: 1 × 15.999 ÷ 35.046 × 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.