Question

If an electric discharge produces 300 liters of ozone (O3), how many liters of oxygen (O2) are required?

3O2->2O3

Answer 1

3O2->2O3

With gases you can use a shortcut and use volumes directly as if volumes were mols. In this case, then, just convert using the coefficients in the balanced equation.
300 L O3 x (3 mols O2/2 mols O3) = 300 x 3/2 = ?

Answer 2

Would it require 450 L of Oxygen?

Answer 3

yes. 3/2 * 200=300

Answer 4

300 x 3/2 = 450