Ozone (O3) can be prepared in the laboratory by passing an electrical discharge through a quantity of oxygen gas (O2): 3 O2 (g) -------> 2 O3 (g) A 10.00-L evacuated steel vessel is filled with 32.00 atm of pure O2 at 25°C. An electric discharge is passed through the vessel, causing some of the oxygen to be converted into ozone. As a result, the pressure inside the vessel drops to 30.64 atm at 25°C. Calculate the final percent by mass of ozone in the vessel.