vapour density

vapour density exists only for gases not for mixtures(solid,liquid)

if for a gas ,
it is simply equal to M/2 where M= molecular mass of mixture

maybe ..

N2O4 =>2NO2
let initially c moles of N2O4
at equillibrium ...

N2O4 = c(1-x)
NO2 = > 2cx

vapour density = M/2
M=totall mass /no. of moles
as mas remains conserved ..

total mass=total mass initially=c(molar mass of N2O4)=c(28+4*16)=92c
no. of moles = c(1-x)+2cx=c(1+x)

hence vapour density = (92c/c(1+x))/2 = 46/(1+x)

Vapour Density is the number of times a gas is heavier than hydrogen.

Vapour Density = mass of a definite volume of gas / mass of same volume of hydrogen.

At STP :

Vapour Density = mass of 22.4 litres of gas / mass of 22.4 litres of hydrogen

→ V.D = molar mass of gas / 2(molar mass of hydrogen)

→ V.D = molar mass of gas / 2 [At STP]

now got the point...........

Thats fine and thats chemistry also :P
Waise well done.
So........