Molecular mass of air = 29?

As air is mainly composed of 80% nitrogen and 20% oxygen
the molecular mass can be calculated as follow
giving the the relative atomic mass of N is 14 and O is 16
i.e. N2 = 14(2) = 28 and O2 = 16(2) = 32
28(0.8)+32(0.2)
= 22.4 + 6.4
= 28.8

It should be called as molar mass rather than molecular mass since air is not a compound.