<span>This would be the atomic mass. In an atom of carbon-12, there are 6 protons and 6 neutrons at rest (electrons have a negligible mass and are usually not part of the overall mass calculation). All atomic masses are based off the measurements of this specific iteration of carbon.</span>
The atomic mass of methane (CH4)is 12 amu for the carbon plus 4 x 1 amu for the four hydrogens, for a total of 16 amu. Therefore, the molar mass of methane is 16g.