Why is the ratio of the mass of carbon to the mass of hydrogen #3:1# with respect to methane?

Question

Peyton Adams · Accepted Answer

Consider the atomic masses of carbon versus hydrogen.

The empirical formula is the #"simplest whole number ratio defining"# #"constituent atoms in a species."# The mass ratio may be different, given that the constituent elements may have vastly different masses. For methane, #CH_4#, the empirical formula is the same as the molecular formula. But for the molecule, we can work out the carbon percentage by mass: #"Mass of 1 mol carbon"/"Mass of 1 mol methane"xx100%=# #(12.011*g*mol^-1)/(16.04*g*mol^-1)xx100%=75%# And clearly, for a binary compound, i.e. 2 elements only, the hydrogen percentage by mass is #25%#. And thus #"mass of carbon:mass of hydrogen"# #=# #3:1# as required.

Noah Aldrich · Answer

undefined The ratio of the mass of carbon to the mass of hydrogen in methane (CH4) is 3:1 because in a methane molecule, there is one carbon atom (with a molar mass of approximately 12.01 g/mol) and four hydrogen atoms (each with a molar mass of approximately 1.01 g/mol). Therefore, the total mass of carbon is approximately 12.01 g/mol, and the total mass of hydrogen is approximately 4.04 g/mol. The ratio of these masses simplifies to approximately 3:1.