I Water bath and water vapor + air mixture in a closed system

Click For Summary
In a vacuum chamber with a water bath and a mixture of air and water vapor, the system reaches equilibrium at room temperature, resulting in 100% relative humidity. At this point, the partial pressure of water vapor matches the saturation pressure dictated by the temperature, as per the Buck equation. The amount of air in the chamber does not affect the water vapor amount, as it is solely dependent on temperature. If the air initially has 0% relative humidity, the pressure will increase to the sum of the air pressure and the water vapor pressure once equilibrium is restored. This highlights the counterintuitive nature of the relationship between air pressure and water vapor in such a closed system.
MacIntoShiba
Messages
7
Reaction score
1
Hello,

At my work I came up with the following question:

Say we have a vacuum chamber. Inside the vacuum chamber we have at the bottom a water bath. The rest of the chamber is filled with a air and water vapor mixture. The whole system is placed in a room, is at room temperature and is in equilibrium.

Since the system is in equilibrium the relative humidity should be 100% (is this correct?). Therefore the partial water vapor pressure should be the same as the water vapor pressure at room temperature (for example given by the Buck equation). This water vapor pressure is only a function of the temperature.

Does this mean that the amount of air (raising the pressure in the vacuum chamber) has no effect on the amount of water vapor inside the vacuum chamber?

Does this mean that if at the start the air has 0% relative humidity (the whole system is still at room temperature) in which case the air pressure is pair will increase to pair + pvapor when the system in back in equilibrium?

I feel like I am missing something.
 
Science news on Phys.org
Yes to all your questions.
 
Reply
  • Like
Likes russ_watters
Its a bit counter intuitive, I would expect the air pressure to play a role here. Thank you for your reply.
 
Reply
  • Like
Likes russ_watters

Thread 'Detection of hot spots with a thermal (non-radiometric) camera'

Hello, We have a thermal camera and its purpose is to detect hot spots at different distances. We made an experiment with a JPEG picture and we noticed the following: At the same distance, one object at 600 degrees and an object at 38 degrees (human body) have the same pixel intensity (255 in grayscale). The image adjusted when the 600 degrees object exited the scene (parts of the human body and background became brighter). We will make a detection algorithm and we need to make sure only...
View full post »

Similar threads

I Is equilibrium vapor pressure different in vacuum and in air?
Replies
2
Views
2K
B Cooling effect of evaporation occurs even if the surroundings are colder?
Replies
10
Views
2K
How does evaporation generate cooling? Swamp coolers edition
Replies
32
Views
4K
I How can visible gas bubbles remain intact inside frozen water?
Replies
8
Views
1K
Vapor pressure -- How does water still boil at 100°C in an open pot?
Replies
35
Views
5K
Phase Equilibrium of Liquid and Vapor Under External Pressure
Replies
9
Views
2K
I Calculating vapor pressure from Boltzmann distribution?
Replies
0
Views
1K
Calculate the amount of water vapor
Replies
3
Views
2K
Thermo: Calculating the temperature drop from gas leaving a system
Replies
11
Views
9K
A practical way to vaporize fuel for high MPG?
Replies
35
Views
937