The percentage composition of carbon by mole in methane is ____?

In one mole of methane, there is one mole of carbon atoms and 4 moles of hydrogen atom.

Therefore, the percentage composition of C by mole in methane will be:

Methane (CH₄CH₄CH₄) is composed of one carbon atom and four hydrogen atoms in each molecule. In one mole of methane, there is one mole of carbon and four moles of hydrogen, making a total of five moles of atoms. 

To determine the percentage composition of carbon by mole, we calculate the mole fraction of carbon, which is the ratio of moles of carbon to the total moles: 15\51. Multiplying this by 100 gives the percentage composition of carbon as 20%. This means that, in methane, carbon contributes 20% of the total moles.

percentage of C=1 mole of C / 5 mole of methane = 1 / 1+4×100 = 20%