Molar MassMolar mass of butane (C4H10)
The molar mass of butane, C4H10, is 58.12 g/mol. One mole of it, which is 6.022 × 1023 molecules, has a mass of 58.12 grams.
About butane
Butane is the other main part of LPG and the fuel in gas lighters. Two compounds, butane and 2-methylpropane, share this formula and molar mass.
The working
The formula C4H10 has 4 carbon atoms and 10 hydrogen 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) | 4 | 12.011 | 48.044 | 82.66% |
| Hydrogen (H) | 10 | 1.0080 | 10.080 | 17.34% |
4 × 12.011 + 10 × 1.0080 = 58.124 g/mol
With the rounded atomic masses used in many school books (C = 12, H = 1) the answer is 58 g/mol. The difference from 58.12 is too small to matter in most school sums.
Percentage composition
By mass, C4H10 is 82.66% carbon and 17.34% hydrogen. The largest share comes from carbon. In a 100 g sample there are 82.7 g of carbon and 17.3 g of hydrogen.
Notice that hydrogen has more atoms in the formula (10) than carbon (4), 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 5 g of C4H10? Divide the mass by the molar mass: 5 ÷ 58.12 = 0.08602 mol.
Moles to grams. What is the mass of 0.25 mol of C4H10? Multiply: 0.25 × 58.12 = 14.53 g.
Counting particles. 5 g contains 0.08602 mol × 6.022 × 1023 = 5.180 × 1022 molecules, and 7.253 × 1023 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 C4H10 is about 58.12 ÷ 22.4 = 2.59 g per litre. Air averages about 29 g/mol, so this gas is heavier than air.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 5.812 g |
| 0.5 mol | 29.06 g |
| 1 mol | 58.12 g |
| 2 mol | 116.2 g |
| 5 mol | 290.6 g |
| Mass | Moles |
|---|---|
| 1 g | 0.0172 mol |
| 10 g | 0.172 mol |
| 100 g | 1.72 mol |
| 1 kg | 17.2 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of C4H10?
The molar mass of butane (C4H10) is 58.12 g/mol, or 58.124 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of C4H10?
100 ÷ 58.12 = 1.72 mol.
What is the mass of one molecule of C4H10?
Divide the molar mass by the Avogadro constant: 58.12 ÷ 6.022 × 1023 = 9.652 × 10-23 g.
What is the percentage of carbon in C4H10?
Carbon makes up 82.66% of the mass of C4H10: 4 × 12.011 ÷ 58.124 × 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.