Chapter 2 - Sections 2.1-2.9 - Exercises - Cumulative Problems - Page 82: 96a

$m(S):m(O)= 2:3$

1. Each molecule of $SO_{3}$ contains 1 atom of S and 3 atoms of O. To get the $S:O$ masses ratio, we need to multiply their relative atomic masses with the number of atoms of each element in the molecule and then reduce the ratio to the smallest possible whole numbers 2. $m(S):m(O) = 32\times1 + 16\times3 = 32:48 = 2:3$