# How do you find the percent composition of all elements in sulfur trioxide?

Mar 20, 2017

Well it is simply the quotient, "mass of component"/"molar mass of compound"xx100%

#### Explanation:

And %S=(32.06*g*mol^-1)/(32.06*g*mol^-1+3xx16.00*g*mol^-1)xx100%

=40%

And what must be %O given %S?

From where did I get the atomic masses in $g \cdot m o {l}^{-} 1$? Did I simply know them off the top of my head?