Science Buddies: "Ask an Expert"

Hi

I have a cylindrical tube of diameter 100 mm and length 1000 mm. The requirement of process is to first remove all the oxygen from the tube by pumping. To break the vacuum (10-3 Pa), it is recommended to fill the tube with inert gas and then open the valves. The problem is i have no gauge that can indicate that the tube is completely filled with gas, so i want to calculate it theoretically. I know that the mass flow rate of my gas is 500 sccm which is equivalent to 500 ccm under standard pressure and temperature conditions. I want to calculate the time required to completely fill the tube with the flow rate of gas?

Hi there,

What is the purpose of this process? It may help for me to know what the goal of your experiment is.

I commonly use inert atmospheres such as argon. Instead of doing calculations to figure out how long it would take to fill the flask, a good way of doing it is to use a balloon to fill the cylinder. I'll tell you what I mean:

If you remove air from the tube with a vacuum, then attach a balloon filled with your inert gas through the valve. You should see that your balloon volume decreases but does not completely deflate, and then stays at a constant volume. This indicates that the atmosphere within your tube has been replaced by your inert gas. If you really want to purge your system of air, you can repeat that process (usually 3x is more than enough), use vacuum again, fill with your inert atmosphere, repeat. The balloon will give you a visual on when the atmosphere has been filled, but this process is usually extremely fast if your tube is under vacuum.

I hope this is a helpful alternative to the calculation you were suggesting.

Let me know if I can provide further assistance.

Erin

hello
i am really struggling with deciding a topic for my chemistry hl internal assessment. i want a hard and a creative topic which can score me a 7 at least. I don't want a simple topic as my teacher has not allowed it. Please help me decide a topic. it shouldn't have an hazardous chemicals and it should be unique and should have a complicated chemistry concept behind it.

Hi there,

Did you try the project selection wizard?

This might be a good place to start!

https://www.sciencebuddies.org/science- ... round-info

Erin