J.R. S. answered • 01/30/18

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Haley,

So far, you're on the right track. You do add all the pressure to get the total pressures. Now, according to Dalton's Law of Partial Pressure, mole fraction of a gas (X) = partial pressure of X/total pressure. You could use PV = nRT and calculate moles of each gas, and then find mole fraction of each, but it's much easier/faster to use Dalton's Law. Thus,

X

_{N2}= 0.32 atm/0.97atm = 0.33X

_{He}= 0.25 atm/0.97 atm = 0.26X

_{CO2}= 0.4 atm/0.97 atm = 0.41You should go ahead and use PV = nRT and see if you don't get the same mole fractions.

Hope this helps.

Haley B.

01/30/18