April 29, 2024, 11:22:21 AM
Forum Rules: Read This Before Posting


Topic: How do I calculate volume of gas that goes from under pressure to a vacuum?  (Read 8278 times)

0 Members and 1 Guest are viewing this topic.

Offline Contextion

  • New Member
  • **
  • Posts: 7
  • Mole Snacks: +0/-0
I have a pressurized vessel of an unknown mixture of gases. The vessel has a positive pressure gauge and is of a known volume. The vessel is connected to a hose which connects to the top of a 1 liter graduated vertical tube - both are filled with water. As the valve to the hose is opened the pressured gas is released and the water is displaced in the hose and some of the cylinder.

If I do this many times with vessels having different pressure and gas mixtures how do I convert all of the volumes I measure on the graduated vertical cylinder to a volume of 1 standardized pressure like 1 atm?

Do i need a gas chromatograph to tell me how many gases I have and if I get a chromatograph how do i figure it out then?

Suppose a 700 psi vessel displaced about 800 ml of water in the cylinder. 200ml of water is still being held above the water line so this creates a vacuum and makes the gases expand. Can this expansion be neglected since the vacuum created from the held water is not great when compared to the initial pressure in the vessel?

Offline Genius

  • Very New Member
  • *
  • Posts: 1
  • Mole Snacks: +0/-0
I have a pressurized vessel of an unknown mixture of gases. The vessel has a positive pressure gauge and is of a known volume. The vessel is connected to a hose which connects to the top of a 1 liter graduated vertical tube - both are filled with water. As the valve to the hose is opened the pressured gas is released and the water is displaced in the hose and some of the cylinder.

IF you have a volume of gas that is going from pressure to vacuum, then you can not have any water. Your system must be defined properly.

If I do this many times with vessels having different pressure and gas mixtures how do I convert all of the volumes I measure on the graduated vertical cylinder to a volume of 1 standardized pressure like 1 atm?

Is the experiment like a barometer? I still don't get it. And how are you trying to get a pressure from a volume? You already measured a pressure above.

Do i need a gas chromatograph to tell me how many gases I have and if I get a chromatograph how do i figure it out then?

You really have no idea what the gasses are going to be, but chromatography may give some helpful hints. In no way will it just spit out what is in there, unless you've got a few million to spend on it, or have access to a badass lab.

Suppose a 700 psi vessel displaced about 800 ml of water in the cylinder. 200ml of water is still being held above the water line so this creates a vacuum and makes the gases expand. Can this expansion be neglected since the vacuum created from the held water is not great when compared to the initial pressure in the vessel?

The water line would imply were a boat floats in the ocean. If you told me that the water line changed in an amount of height it would make more sense. Look at how a mercury barometer works, is it what you are trying to do? I think the fact that the pressure goes from one vessel to another is irrelevant, you seem to only care about the final state.

Offline Contextion

  • New Member
  • **
  • Posts: 7
  • Mole Snacks: +0/-0
The pressure goes from one vessel to another and then vanishes. The pressure becomes negative to the amount of being able to hold the water as it does.

The water at the top of the column exerts more pressure than that near the bottom so I need to integrate the height with the density and area some how so I can set it equal to the amount of vacuum.

If the pressurized gases displaced exactly all of the water in the column so that the water line inside and outside of the column were equal then the pressure inside and outside would also be equal at 1 atm.

Offline Contextion

  • New Member
  • **
  • Posts: 7
  • Mole Snacks: +0/-0
Can someone please tell me the integral to perform that sets a volume of a liquid substance equal to a pressure?

Sponsored Links