How to Calculate Humidity in an Airtight Vessel?

[mahler.ji]

Hello,

This is my first post on here, so thank you in advance for your help.

Homework Statement

I have an air tight vessel that has a volume of 1m^3. The bottom of the vessel has water in it. What internal pressure is needed inside the vessel to achieve a temperature of 45C and 75% Relative Humidity? Also, what is the partial pressure of water vapor at that condition?

Homework Equations

None Given.

The Attempt at a Solution

I can't figure out how to figure out the mass/moles of water vapor in the air in order to figure out partial pressure and, thus, the relative humidity. I can't figure out how to get the overall pressure without knowing the mass/moles of water vapor in the air either. So I just need to know how to get started and i think I can finish it.


again, thanks for your help.

 

[mahler.ji]

Anyone have any ideas at all?

I think the real question is, based on Temperature and Pressure, how do I know how much water is in the air??

Thanks,