Making a Uniform Mixture of Helium Gas

In summary, the conversation discusses an experiment involving a dilute isotopic mixture of helium gas in a spherical vessel. The question asks for an estimate of the time needed for a uniform mixture to form, as well as a suggestion for a better method. The equations used include the area formula for a sphere, the ideal gas law, Fick's law of diffusion, and the mass flux equation. The solution involves finding the area first and then using it to calculate the length, which can be plugged into Fick's equation. The poster eventually figures out the answer after multiple attempts.
  • #1
ibysaiyan
442
0
1.
Homework Statement
Question
This is an experiment on a dilute isotopic mixture of helium gas. A spherical vessel of
diameter 1 m is first filled with 4He gas to one atmosphere pressure. Then a small
amount of 3He gas is introduced through a valve on one side of the vessel. Make a
rough estimate of how long one must wait before a uniform mixture has formed (use
the result for the time dependence of the root mean square travel distance in a
random walk in 1D.) Suggest a better way to make a uniform mixture.

Homework Equations



Area = pi (diameter/2)^2 , pv =nrt , ficks law of diffusion , Mass flux = 1/3lv

The Attempt at a Solution


I am not sure where to start from. I am reading about fick's law of diffusion right now however I'd love tobe pointed out in the right direction.

Since the question asks for time dependence then isn't second law the most obvious equation to use ?
edit: hm.. as i was reading i came across this idea.. how about i get the area first, then divide volume by area to give me the 'length' which i can plug into ficks equation if I am not mistaken.
Appreciate your help.
 
Last edited:
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  • #2
Anyone?
 
  • #3
Never mind.. can one of the moderators please close this thread. I have figured out the final answer,etc.. took me countless sheets but it was worth it.
 

1. How do you make a uniform mixture of helium gas?

In order to make a uniform mixture of helium gas, you will need to use a gas cylinder and a gas regulator. First, attach the regulator to the top of the cylinder and make sure it is securely attached. Then, open the valve on the cylinder and adjust the regulator to the desired pressure. This will allow the helium gas to flow into the mixture evenly.

2. What is the ideal pressure for a uniform mixture of helium gas?

The ideal pressure for a uniform mixture of helium gas will depend on the specific application and the desired concentration of helium. Generally, a pressure of 1 atmosphere (14.7 psi) is recommended for most applications.

3. Can I mix helium gas with other gases to create a uniform mixture?

Yes, helium gas can be mixed with other gases such as oxygen or nitrogen to create a uniform mixture. However, it is important to carefully calculate the ratios and pressures of each gas in order to achieve a truly uniform mixture.

4. What is the best way to ensure a uniform mixture of helium gas?

The best way to ensure a uniform mixture of helium gas is to use a gas mixer or blender. This device will accurately measure and mix the desired gases to create a precise and uniform mixture. It is also important to regularly check and adjust the pressure and flow rates to maintain the uniformity of the mixture.

5. How long will a uniform mixture of helium gas last?

The longevity of a uniform mixture of helium gas will depend on the specific application and storage conditions. In general, helium gas has a long shelf life and will remain in a uniform mixture as long as it is stored properly in a sealed container. It is important to regularly check the pressure and quality of the gas to ensure it is still suitable for use.

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