The vapour density of a mixture containing NO2 and N2O4 is 27.6. Mole fraction of NO2 in the mixture is:
Let the moles of NO2 be x.
So, moles of N2O4 will be 1−x.
We know that, Molar mass = 2×vapour density
So, Molar mass = 2×27.6 = 55.2 g
Molar mass of NO2 = 46 g and N2O4 = 92 g
x×46+(1−x)×921 = 55.2
= 46x+92−92x=55.2
On solving, x=36.846=0.8
∴ mole fraction of NO2 will also be 0.8 and mole fraction of N2O4 will be 0.2.