The density of air is 0.001293 g/cm3 at STP. Identify which of the following statements is correct:-
a) Vapor density is 14.48.
b) Molecular weight is 28.96.
c) Vapor density is 0.001293.
4) Vapor density and molecular weight cannot be determined.

STP condition means one mole of air at 0 degree Celsius and 1 ATM pressure has 22.4 litres of volume
Now this 22.4 litres is actually 22400 ml which means cm^3

Using density we can easily convert this into the mass of air in 22400 ml of volume


22400 cm^3 *.001293g/1 cm^3
=  28.96 g
This is the mass of 1 mole of air at STP which is also called as the molar mass.