Average molar weight (Molecular weight): or Mean Molecular Mass

We know that for gas:

Pressure fraction = Mole fraction= Volume fraction

Pressure % = Mole % = Volume %

Consider mixture of two different gases (A) and (B) and their moles nA

and nB

Illustrated Examples:

(1) A sample of ozone gas is found to be 40% dissociated into oxygen. The average molecular mass of sample should be :

(2) Vapour density of mixture of NO2 ​and N2O4 ​ is 34.5, then percentage abundance of NO2 ​ in mixture is:

(3) A gaseous mixture of H2 ​and CO2 ​contains 66 mass % of CO 2 ​ The vapour density of the mixture is:

(4) The vapour density of a mixture containing NO2 and N2O4 is 27.6 . Mole fraction of NO2 in the mixture is:

(5) N2O4 on decomposition gives its monomer NO2 and they are found to be in equilibrium at 300 K. if the VD of such a mixture is 41.4 the calculate % composition by (1) Moles of NO2 and N2O4 (2) By mass O2

(6) A compound of nitrogen and oxygen was found to contain 7: 16 by mass N and O respectively. Calculate molecular formula if vapour density is 46.

(7) A mixture of blue and green balls contains 25% by number blue balls. Mass of each blue balls is 40 gm and mass of each green balls is 20 gm calculate (1) Average mass of ball (2) % by mass

(8) Air contains 20% of O2 and 80 % N2 by moles find the average molecular mass weight and % by mass of oxygen and nitrogen.