The molar mass of methane (CH4) is 16.043 g/mol.
Case matters: CO is carbon monoxide, Co is
cobalt. Brackets and hydrates are fine — try
or
.
| Element | Atoms | Atomic mass | Mass contributed | Percent |
|---|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 | 74.87% |
| Hydrogen (H) | 4 | 1.0080 | 4.032 | 25.13% |
| Total | 5 | 16.043 | 100.00% |
12.011 + 4.032 = 16.043 g/mol
Grams and moles
25 g of methane is 1.558 mol, because 25 ÷ 16.043 = 1.558.
These elements have no single atomic weight. Their isotopic mix varies slightly depending on where on Earth the sample came from, so the figure used here is the conventional value IUPAC publishes for when one number is needed: carbon is 12.011, and really lies between 12.0096 and 12.0116; hydrogen is 1.0080, and really lies between 1.00784 and 1.00811.
Methane is the simplest hydrocarbon and the bulk of natural gas. At 16.043 g/mol it is among the lightest molecules a course handles regularly, and lighter than air, which averages about 29 g/mol. That density gap explains why a methane leak rises to ceiling level while a propane leak pools on the floor.
Carbon holds 74.87% of the mass despite being one atom in five. Hydrogen is light enough that four of them together contribute only 4.032 g/mol.
That high hydrogen fraction is why methane burns cleanest of the fossil fuels per unit of energy. Each molecule yields one CO2 and two H2O, so a greater share of the energy released comes from forming water rather than carbon dioxide. Set it beside coal, which is mostly carbon with very little hydrogen, and the difference in carbon dioxide per joule follows straight from these mass fractions.