What is the formula weight of methane?
Though we call this relative formula MASS not weight
First we need to know Methanes molecular formula.
This means one molecule of methane contains one carbon atom and four hydrogen atoms.
The formula mass of a molecule is the total of all relative atomic masses for each atom added together.
So in this case;
C = 12
H = 1 ( x 4 as we have 4 hydrogen atoms) = 4
(12 + 4)