# Given the balanced equation, 2SO_2 + O_2 -> 2SO_3 , what is the molar ratio of O_2 to SO_3?

One mole of ${O}_{2}$ will produce two moles of $S {O}_{3}$, so the mole ratio is 1:2.
If one mole of ${O}_{2}$ gives you 2 moles of $S {O}_{3}$, then the mole ratio between ${O}_{2} : S {O}_{3}$ is 1 : 2