[D_Alex]

Natural gas is a mixture of methane and heavier hydrocarbons, the composition varies by region, depending largely on how the LPGs (propane and butane) are used. Ethane usually ends up in natural gas, unless there is a petrochemical complex nearby.

So, 80% is a theoretical maximum, which is never achieved in practice. 75% hydrogen looks pretty right.

[thaumasiotes]

I'm still curious about the measurement "on a molar basis". If you have 20 moles of methane, and you process that to separate out the carbon, you'll end up with 20 moles of some form of carbon and 40 moles of hydrogen gas, right?

[philipkglass]

I think that "on a molar basis" is there to clarify that it's counting by number of atoms rather than grams. On a gram-for-gram basis, methane is ~75% carbon.

[D_Alex]

"Molar" refers to a number of elementary entities, which could be atoms or molecules or w/e. So yes, if you are counting moles of H2 gas, but not if you are counting atoms...