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# amount of helium needed to fill a balloon

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So I am working on a project for class, I am needing a compact helium solution to launch a balloon off of a sea kayak.

I found these

http://www.lelandgas.com/helium_filled_cylinders.htm

Its a 5 inch 95 cc 2.5 gram helium canister.

I have been told that one of these will fill an 18 inch balloon up

I am trying to figure out how many of these canisters I will need to fill a 24 inch or 36 inch balloon.

Any help would be great, its been forever since I have done these calculations.

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bump

I emailed the company that makes those canisters, they couldn't tell me either

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Assuming the balloons are spherical, which they aren't, you can use Volume = (4/3)πr^3 to work it out.

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hey all i needed to bump this thread and wanted to see if there were any science guys on here since I have been unable to get in contact with one at my school today

So I have an 18" mylar balloon that takes .5 cubic feet of helium to fill

I also have the above helium canister which also has .5 cubic feet of helium, enough to fill this balloon.

now being that I want to fill up the balloon and raise it with out it being attached to the tank I have opted to use a thin rubber tube to sent the helium through.

my tubing is about 8 feet long.

My question is how does helium work in this situation. If the canister is emptied and the helium goes through the tubing to the balloon will helium reside in the tubing or will it all float up to the balloon. The tubing is acting as my tether. If I need to explain this better let me know

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I think I got the idea of what your trying to do if not correct me. Since helium is less denser than air it will go up thats the main reason as to why you are using helium. But in this case some other measurements such as the radius of the tube is needed to get it's volume. Let's assume that we know it. Since the canister has the EXACT amount of helium needed to fill I would suggesting a bigger one at least 0.6 incase If some helium gets trapped inside the tube. That's what I understood.

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thats correct and also the issue. The canisters I ordered are the only ones on the market right now. Each canister is about \$20. I know I am going to have to do some testing, but also don't want to waste to many of them. The main thing is trying to figure out if that .5 cubic feet of helium will rise all the way to the balloon or just try to equalize between the tubes and the balloon

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For a 24" balloon, you'll need three (technically, 2.4, but good luck buying 0.4 of a canister). For a 36" balloon, you'll need 8.

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yeah i figured that was the case, now I just need to figure out the tubing issue

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Hi,

I haven't got time to work through the question, but there are different types of "amounts" -do you mean volume?

The equation you can use to work out volume is like this:

v =nRt/p

v = volume in metres cubed (times by 10^-6 to get cm3)

n = number of moles

moles = mass of gas, in grams/Ar of gas, taken from the periodic table

R = ideal gas constant (usually taken to be 8.31)

t = temperature in Kelvin (kelvin = degrees celcius plus 273)

p = pressure in kilopascals.

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thanks for the equations, this will help, but I think right now I am set on using just one or 2 tanks to reach the balloon size I need. Its the tubing situation that I am trying to figure out

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thanks for the equations, this will help, but I think right now I am set on using just one or 2 tanks to reach the balloon size I need. Its the tubing situation that I am trying to figure out

The main thing is trying to figure out if that .5 cubic feet of helium will rise all the way to the balloon or just try to equalize between the tubes and the balloon

Well, if the volume of your container is greater than 0.5 cubic feet, and have 0.5 cubic feet of helium in there, the helium will mix in with air already in it initially, but separate so helium is at the top. If the containers are empty, then the helium will fill the containers , thus reducing pressure and temperature.

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thats correct and also the issue. The canisters I ordered are the only ones on the market right now. Each canister is about \$20. I know I am going to have to do some testing, but also don't want to waste to many of them. The main thing is trying to figure out if that .5 cubic feet of helium will rise all the way to the balloon or just try to equalize between the tubes and the balloon

What I would say is get two of those canisters and try it out for your self you can't do everything theoritcally you need to do some practically as well. I said to get two cause just in case if there were human errors who knows we are not perfect.

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