Molar MassMolar mass of propane (C3H8)
The molar mass of propane, C3H8, is 44.10 g/mol. One mole of it, which is 6.022 × 1023 molecules, has a mass of 44.10 grams.
About propane
Propane is a fuel gas that turns liquid under moderate pressure. It is one of the main parts of LPG.
The working
The formula C3H8 has 3 carbon atoms and 8 hydrogen atoms, 11 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 | 81.71% |
| Hydrogen (H) | 8 | 1.0080 | 8.064 | 18.29% |
3 × 12.011 + 8 × 1.0080 = 44.097 g/mol
With the rounded atomic masses used in many school books (C = 12, H = 1) the answer is 44 g/mol. The difference from 44.10 is too small to matter in most school sums.
Percentage composition
By mass, C3H8 is 81.71% carbon and 18.29% hydrogen. The largest share comes from carbon. In a 100 g sample there are 81.7 g of carbon and 18.3 g of hydrogen.
Notice that hydrogen has more atoms in the formula (8) than carbon (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 40 g of C3H8? Divide the mass by the molar mass: 40 ÷ 44.10 = 0.9071 mol.
Moles to grams. What is the mass of 3 mol of C3H8? Multiply: 3 × 44.10 = 132.3 g.
Counting particles. 40 g contains 0.9071 mol × 6.022 × 1023 = 5.463 × 1023 molecules, and 6.009 × 1024 atoms in all.
As a gas. At 0 °C and 1 atmosphere one mole of an ideal gas occupies 22.4 litres, so the density of C3H8 is about 44.10 ÷ 22.4 = 1.97 g per litre. Air averages about 29 g/mol, so this gas is heavier than air.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 4.41 g |
| 0.5 mol | 22.05 g |
| 1 mol | 44.1 g |
| 2 mol | 88.19 g |
| 5 mol | 220.5 g |
| Mass | Moles |
|---|---|
| 1 g | 0.02268 mol |
| 10 g | 0.2268 mol |
| 100 g | 2.268 mol |
| 1 kg | 22.68 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of C3H8?
The molar mass of propane (C3H8) is 44.10 g/mol, or 44.097 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of C3H8?
100 ÷ 44.10 = 2.268 mol.
What is the mass of one molecule of C3H8?
Divide the molar mass by the Avogadro constant: 44.10 ÷ 6.022 × 1023 = 7.322 × 10-23 g.
What is the percentage of carbon in C3H8?
Carbon makes up 81.71% of the mass of C3H8: 3 × 12.011 ÷ 44.097 × 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.