Posted by Rajiv on .
A mixture contains n2o4 and No2 in the ratio 2:1 by volume what is the vapour density of the mixture.Pls answer the question i have been on the question for 2 hrs by now tried solving using mole fraction ideal gas equation an using the formula molar mass /2 but still couldn't get the answer ans as is written is 38.3 pls tell how .explain in detail may be

Physical chemistry 
DrBob222,
I think the trouble you are having is knowing what vapor density is. vapor density = molar mass gas/molar mass H2.
vapor density N2O4 = molar mass N2O4/molar mass H2 = 92.011/2.016 = 45.64
vapor density NO2 = molar mass NO2/molar mass H2 = 46.0055/2.016 = 22.82
The ratio is 2:1 in favor N2O4; therefore,
v.d. N2O4 x 2 = 91.28
+ v.d. NO2 x 1 = 22.82
sum is 114.1
average is 114.1/3 = 38.033 which rounds to 38.03.