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?

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...2) = x(O2)*p

where p(O2) is partial pressure of O2 in the mixture, x(O2) is mole fraction of oxygen in the mixture and p is total pressure of mixture. Hence:

x(O2) = p(O2)/p = 0.25 or 25%.

To find mass percent we have to convert moles ...