Molar MassMolar mass of glycerol (C3H8O3)
The molar mass of glycerol, C3H8O3, is 92.09 g/mol. One mole of it, which is 6.022 × 1023 molecules, has a mass of 92.09 grams.
92.09 g/mol
3 × 12.011 + 8 × 1.0080 + 3 × 15.999 = 92.094 · 14 atoms in the formula · also called glycerine, propane-1,2,3-triol
About glycerol
Glycerol is a sweet, syrupy liquid with three OH groups, obtained as a by-product of soap making.
Other names: glycerine, propane-1,2,3-triol.
The working
The formula C3H8O3 has 3 carbon atoms, 8 hydrogen atoms and 3 oxygen atoms, 14 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Carbon (C) | 3 | 12.011 | 36.033 | 39.13% |
| Hydrogen (H) | 8 | 1.0080 | 8.064 | 8.76% |
| Oxygen (O) | 3 | 15.999 | 47.997 | 52.12% |
3 × 12.011 + 8 × 1.0080 + 3 × 15.999 = 92.094 g/mol
With the rounded atomic masses used in many school books (C = 12, H = 1, O = 16) the answer is 92 g/mol. The difference from 92.09 is too small to matter in most school sums.
Percentage composition
By mass, C3H8O3 is 39.13% carbon, 8.76% hydrogen and 52.12% oxygen. The largest share comes from oxygen. In a 100 g sample there are 39.1 g of carbon, 8.8 g of hydrogen and 52.1 g of oxygen.
Notice that hydrogen has more atoms in the formula (8) than oxygen (3), 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 250 g of C3H8O3? Divide the mass by the molar mass: 250 ÷ 92.09 = 2.715 mol.
Moles to grams. What is the mass of 0.2 mol of C3H8O3? Multiply: 0.2 × 92.09 = 18.42 g.
Counting particles. 250 g contains 2.715 mol × 6.022 × 1023 = 1.635 × 1024 molecules, and 2.289 × 1025 atoms in all.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 9.209 g |
| 0.5 mol | 46.05 g |
| 1 mol | 92.09 g |
| 2 mol | 184.2 g |
| 5 mol | 460.5 g |
| Mass | Moles |
|---|---|
| 1 g | 0.01086 mol |
| 10 g | 0.1086 mol |
| 100 g | 1.086 mol |
| 1 kg | 10.86 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of C3H8O3?
The molar mass of glycerol (C3H8O3) is 92.09 g/mol, or 92.094 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of C3H8O3?
100 ÷ 92.09 = 1.086 mol.
What is the mass of one molecule of C3H8O3?
Divide the molar mass by the Avogadro constant: 92.09 ÷ 6.022 × 1023 = 1.529 × 10-22 g.
What is the percentage of oxygen in C3H8O3?
Oxygen makes up 52.12% of the mass of C3H8O3: 3 × 15.999 ÷ 92.094 × 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.