Chemistry Numerical? Any chemitry genius?

Question

40% of N2O4 molecules are dissociated in a sample of gas at 27 degree celcius and 760 torr. The density of equilibrium mixture is
1) 2.7g/l 2) 2.8 g/l 3) 3.9 g/l 4) 4.9 g/l

Answer 1

1) 2.7 g/l
pV=nRT, so n/V = p/RT
n/V=1,013*10^5 [Pa] / 8,314 [J/mol*K] * 300 [K]
n/V = 40,61 mol/m^3 = 0,04061 mol/l
let you have got 1 l of this mixture, there is 0,04061 mol of molecules. Before the dissociation there was X mol of N2O4, After the dissociation - 0,6X mol of N2O4 and 0,8X mol of NO2 (0.4X N2O4 dissociated, so 0.8X NO2 was formed).
0.6X + 0.8X = 0,04061
so 0.6X =0,0174mol of N2O4
0,8X = 0.0232mol of NO2
you can count the mass in g
1,07 g of NO2 and 2,67 g of N2O4 so it is 2,7 g of gas
And this 2,7g is in 1l. So the denisity is 2,7g/l

Answer 2

92g/22.4L =