Nitrogen dioxide (NO2) cannot be obtained in a pure form in the gas phase because it exists as a mixture of NO2 and N2O4. At 23°C and 0.94 atm, the density of this gas mixture is 2.6 g/L. What is the partial pressure of each gas?

Question

NO2
N2O4

Answer 1

P*molar mass = d*RT
Substitute and solve for the "average molar mass" of the mixture. d in the above formula is density in g/L.
Then let
X = fraction that is NO2
1-X = fraction that is N2O4
-------------------
X(molar mass NO2) + (1-X)(molar mass N2O4) = avg molar mass mixture.
Solve for X and 1-X.
Then pNO2 = X*0.94 = ? atm.
and pN2O4 = (1-X)*0.94 = ? atm

Answer 2

PNO2 = 0.53atm
PN2O4 = 0.45atm