I want to know how many water molecules are in one cubic meter of air (Relative humidity=20%, Temperature=293K)
This is my calculation:
$p=2.3kPa$ (because of vapor pressure at 20C is 2.3 kPa (as on wikipedia https://en.wikipedia.org/wiki/Vapour_pressure_of_water)
Now I multiply n by $N_A$ and then by 0.2 (because relative humidity is 20%)
Is my approach reasonable?