Question

Use simple calculation to show that moist air is lighter than dry air?

Answer 1

density of dry air = p/(r*t)

where p = pressure, r = gas constant for dry air, t = temperature in K

density of dry air + H2O = p/(r*t) + p1/(r1*t1)

where p1 = pressure of water vapour, r1 = gas constant for water vapour,

t1 = temperature in K of water vapour

THEREFORE, we know,

r < r1

since r1 is 461.495 J/K and r is 287.03 J/K

So, density of dry air > density of moist air

(p/(287.05 J*K) > p/(491.495 J*K))

Hope you found this helpful :)