Question

Q. If the components of air are $N_2,78\%;O_2,21\%;Ar,0.9\%andC{O}_2,0.1\%byvolume,whatwouldbethemolecularweightofair?$

Answer 1

Dry air is a mixture of gases where the molecular weight can be calculated by adding the weight of each component.As shown below:
Wt of each component is calculated by multiplying the % wt. of each component with moleculat wt.
(0.78) x (28 g N₂/mol) + (0.21) x (32 g O₂/mol)) + (0.009) x (40 g Ar/mol) + (0.001) x (44 g CO₂ /mol)

= 21.84 + 6.72 + 0.36 +0.044 = 28.964 g/mol

molecular weight of air =28.964 g/mol