The density of air is 0.001293 g/cc at S.T.P. Its vapour density is ___________.

I mole of air has 22400 mL. Mass of air is:

$\mathrm{Density}=\frac{\mathrm{Mass}}{\mathrm{Volume}}$

$\mathrm{Mass}=0.001293\times 22400=28.96 \mathrm{g}$

Using the formula:

$\mathrm{Molecular} \mathrm{mass}=\mathrm{Vapor} \mathrm{density}\times 2$

$\mathrm{Vapor} \mathrm{density}=\frac{28.96}{2}=14.48 \mathrm{gm}$