How can I mix gases in a chamber measuring only pressure and temperature

  • #1
electr0dave
3
0
Hello all!

Basically I intend to create an environment inside a chamber with variations of CO2 percentages, using electrovalves.
The mixing gas is always compressed air + CO2.

For example: create a 50% CO2 concentration with a total pressure of 2 Bar.
The chamber is closed, and compressed air is introduced up to 1 bar. Then CO2 is introduced until Ptotal reaches 2 bar.

The problem is that with this gas mixture, the chamber will be heated until 50°C, varying the pressures inside.

Can someone help me with some calculations? I am an electronics engineer and so chemistry and thermodynamics aren't my strong ones.

PS: The chamber will have an unknown volume, given that inside it will be placed parts also of variable volume.
 

Answers and Replies

  • #2
22,338
5,206
What is the initial state of the pure gases and what is the final state of the mixture?
 
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  • #3
electr0dave
3
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Hello. Thanks for the reply.

Initially the chamber has air at ambient pressure.
I fill the chamber with compressed air (coming from a compressor) to 2 bar and then close the solenoid valve and open an electrovalve that only escapes that air (until pressure "0"). A kind of renewal cycle.
Then I open the valve of the compressed air again until P1, close it, and open the valve of the CO2 cylinder until the pressure P2.

Inside the chamber will be an object that absorbs CO2. The aim is to control and monitor the pressure inside the chamber.

By measuring the total pressure variation I must get a good approximation (knowing that the object only absorbs CO2) from how much CO2 was absorbed.
 
  • #4
22,338
5,206
Hello. Thanks for the reply.

Initially the chamber has air at ambient pressure.
I fill the chamber with compressed air (coming from a compressor) to 2 bar and then close the solenoid valve and open an electrovalve that only escapes that air (until pressure "0"). A kind of renewal cycle.
Then I open the valve of the compressed air again until P1, close it, and open the valve of the CO2 cylinder until the pressure P2.

Inside the chamber will be an object that absorbs CO2. The aim is to control and monitor the pressure inside the chamber.

By measuring the total pressure variation I must get a good approximation (knowing that the object only absorbs CO2) from how much CO2 was absorbed.
If you don't know the volume available for gas in the system, you won't be able to get the absolute amount of CO2 absorbed...only the fraction of the CO2 absorbed. Also, P2 must of course be higher than P1.

Are you familiar with the ideal gas law?
 
  • #5
electr0dave
3
0
If you don't know the volume available for gas in the system, you won't be able to get the absolute amount of CO2 absorbed...only the fraction of the CO2 absorbed. Also, P2 must of course be higher than P1.

Are you familiar with the ideal gas law?

Hello.
I need to distinguish which object absorbs more CO2. So a comparison of fraction is sufficient.

As for the pressure P2, I wanted to refer to the pressure above P1.
Therefore, in the example, P1 = 1bar and P2 = Ptotal = 2bar (or 1 bar above P1).

I am familiar with the ideal gas law.
Can I take the volume out of the equation? It will be the same in both gases ... just like the temperature.
But the temperature will affect the gases in different ways, right? It will depend only on the ratio of the number of moles ...

I can understand this in my head, but I can not find a mathematical basis for the problem ...
 
  • #6
22,338
5,206
Hello.
I need to distinguish which object absorbs more CO2. So a comparison of fraction is sufficient.

As for the pressure P2, I wanted to refer to the pressure above P1.
Therefore, in the example, P1 = 1bar and P2 = Ptotal = 2bar (or 1 bar above P1).

I am familiar with the ideal gas law.
Can I take the volume out of the equation? It will be the same in both gases ... just like the temperature.
But the temperature will affect the gases in different ways, right? It will depend only on the ratio of the number of moles ...

I can understand this in my head, but I can not find a mathematical basis for the problem ...
Please give it a shot. Let V be the volume of the chamber and T be the temperature, and do everything algebraically. Let's see what you come up with. If you have trouble, I'll help.
 

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