What is the mass of liquid water in 1 cubic meter of 100% saturated air?

Question

I also need some mathematical relation to calculate that.

Answer 1

Specific humidity is the mass of water vapor per unit mass of moist air. Specific humidity = mass of water vapor / mass of dry air. The mean molecular mass of dry air is a constant given as about 4.81*10^-26 kg.

So...

1 = m / 4.81*10^-26
m = 4.81*10^-26 kg

That's how I would solve it at least, but thats assuming the molecular mass of the water vapor is the same as dry air in order to achieve 100% saturation, which isn't necessarily the case. It does vary by temperature and pressure, and I think a chart is probably the easiest way to get values (although I remember having to calculate them in atmospheric thermo).

There's also a relationship using partial pressures...

q = (0.622*partial pressure of water vapor)/(atmospheric pressure of moist air - partial pressure of water vapor).

Answer 2

It depends on the temperature of the air.

You can look up the mass of water in air at any temperature and saturation using a "psychrometric chart". The mathmatical relation between air mass, water mass, temperature, and saturation is pretty complex.

This link is to an on-line psychrometric chart:
http://www.sp.uconn.edu/~mdarre/NE-127/NewFiles/psychrometric_inset.html

Answer 3

try looking up steam tables. It's been awhile since i had to know this stuff but I believe that's where you'll find that info.