Ozone (O3) can be prepared in the lab by passing an electrical discharge through a quantity of oxygen gas (O2).

3 O2 (g) ---> 2 O3 (g)

An evacuated steel vessel with a volume of 10.00 liters 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.