Determining the initial mole and mass fractions of oxygen and nitrogen in a mixture using Dalton's law of partial pressure. Solution in MS Word.

A reaction vessel contained 5 liters of a mixture of N2 and O2 gases at 25oC and 2 atm pressure. The oxygen in the mixture was completely removed by causing it to oxidize with an excess of electrically heated zinc wire contained in the vessel to non-volatile solid ZnO. The pressure of N2 that remained (measured again at 25oC) was 1.5 atm. What were the mole and mass percent of O2 in the starting mixture?