When 7.50 l of sulfur trioxide are produced by the reaction of sulfur dioxide in an excess of oxygen at standard temperature and pressure, how many liters of sulfur dioxide were used? 2so2 (g) + o2 (g) yields 2so3 (g)?

Explanation:

For this problem,  we must use Gay-Lussac's Law of  Combining Volumes:

The ratio in which gases react is the same as the ratio of their coefficients in the balanced equation.

The balanced equation is

Theor: 2 L                2 L  

         2SO₂ + O₂ ⟶2 SO₃

V/L:                           7.50

Gay-Lussac's Law tells us that 2 L of SO₂ form 2 L of SO₃.

The volume of SO₂ used was