Why dry air is heavier than moist air?

Explanation

The average molecular mass of dry air is
`"M(dry air)"=(%" of "N_(2)xx28+%" of "O_(2)xx32)/(100)`
Average molecular mass of wet air is
`"M(wet air)"=(%" of "N_(2)xx28+%" of "O_(2)xx32+5" of "H_(2)Oxx18)/(100)`
Therefore, molecular mass of dry air will be more than than the molecular mass of wet air.
Since molecular mass of dry air is more than that of wet air, it is heavier.