Sciencemadness Discussion Board - He vs H

He vs H

MineMan - 8-2-2021 at 14:10

H has always been preferred in lighter than air craft because it is the lightest gas. But it is H2 while He is He. So would not their mass be the same for a given volume. What am I missing?

Antigua - 8-2-2021 at 14:16

Not sure what you mean exactly, but in standard conditions of pressure and temperature helium has density of 4g/22.4dm^3 and hydrogen is 2g/22.4dm^3. Helium would be a great light gas if not for it's price (it's becoming more and more scarce and hard to get!). Other than that it's better than hydrogen in almost everything. It's not flammable and won't explode due to a spark, it's still much lighter than air and safer to handle.

Morgan - 8-2-2021 at 14:27

Neutrons

draculic acid69 - 8-2-2021 at 20:19

I think that you are over thinking it

draculic acid69 - 8-2-2021 at 20:27

Also how do we know any noble gases molar mass precisely? It's not like they form compounds that can be weighed.apart from there position on the periodic table where there located giving us a number thats more than the one on the left and less than the one on the right how do we know for sure the exact number of there molar mass?

zed - 8-2-2021 at 20:51

Ummm. Helium is a mono-atomic gas. Hydrogen is diatomic. Were it not for this disparity, the numbers would be very different. If Helium were diatomic, a mole of Helium Gas, would be twice as heavy as it is, and 4 times the density of hydrogen, rather than approximately double.

Seems like there might be more Helium around, than we suspect. Might be inert, but it seems to have an affinity for metals. Likes to "stick" to them. But, I'm gonna check on that.

https://www.forbes.com/sites/quora/2016/01/01/why-we-are-run...

OK. Maybe not useful this one? Possible hydrogenation catalyst? http://etd.fcla.edu/CF/CFE0000660/Oztek_Muzaffer_T_200508_MA...

OK. The quest goes on.

Is some of that Helium hiding in plain sight?

I'm not having any luck. Though there is actually plenty of Helium in the Atmoshere. Just very expensive to isolate.

Cheaper to get it from the ground.

[Edited on 9-2-2021 by zed]

[Edited on 9-2-2021 by zed]

DraconicAcid - 8-2-2021 at 21:01

Quote: Originally posted by draculic acid69

Also how do we know any noble gases molar mass precisely? It's not like they form compounds that can be weighed.apart from there position on the periodic table where there located giving us a number thats more than the one on the left and less than the one on the right how do we know for sure the exact number of there molar mass?

Mass spectroscopy can measure it to many decimal places.

draculic acid69 - 9-2-2021 at 00:51

Quote: Originally posted by DraconicAcid

Quote: Originally posted by draculic acid69

Mass spectroscopy can measure it to many decimal places.

Didnt know that.U learn something new everyday.
Without mass spectrometry would we have other ways
to figure it out or would we still be guestimating and before
MS did we have a number that was close Or in the ballpark?

[Edited on 9-2-2021 by draculic acid69]

Fulmen - 9-2-2021 at 00:59

There are physical processes where atomic weight play in. Diffusion is one classic example, this is how they separated U235 from U238 during WWII.

DraconicAcid - 9-2-2021 at 02:54

Quote: Originally posted by draculic acid69

Quote: Originally posted by DraconicAcid

Quote: Originally posted by draculic acid69

Mass spectroscopy can measure it to many decimal places.

With helium in particular, Rutherford measured the charge-to-mass ratio of alpha particles, giving a fairly precise atomic mass as soon as he proved that they were helium nuclei.

CharlieA - 9-2-2021 at 17:25

For any gas, you can measure the pressure, volume and temperature of a given mass of gas and calculate the molar mass from the ideal gas law: PV=(wt of gas/MW)RT, solving for MW.

Texium - 9-2-2021 at 18:20

Quote: Originally posted by CharlieA

For any gas, you can measure the pressure, volume and temperature of a given mass of gas and calculate the molar mass from the ideal gas law: PV=(wt of gas/MW)RT, solving for MW.

Yep, that's how it was done in the really old days. It's just an estimate since gases aren't ideal, but helium is about as close as you can get in real life to an ideal gas, so it's a decent approximation for it.

CharlieA - 10-2-2021 at 17:50

Quote: Originally posted by Texium (zts16)

Quote: Originally posted by CharlieA

For any gas, you can measure the pressure, volume and temperature of a given mass of gas and calculate the molar mass from the ideal gas law: PV=(wt of gas/MW)RT, solving for MW.

I believe most gases approach ideal behavior at low P and high V, so the conditions you can operate at and get significant measurements is important.

As for as "really old days", I will be 81 on March the 6th

And for what it is worth, it is only a vicious rumor that I was an assistant in Robert Boyle's laboratory

Aloesci - 11-2-2021 at 08:06

If i remember correctly, 1 mole of a gas fills about 22L of volume at 1atm, regardless of it's Mr/Ar.

1 mole of He has about 2 times the mass as 1 mole of hydrogen because He has 2 protons and 2 neutrons, whereas a H2 molecule has 2 protons.

I say about because gasses rarely behave in an "ideal way" and other factors affect how the behave, but its a good approximation -> PV=nRT .

[Edited on 11-2-2021 by Aloesci]

[Edited on 11-2-2021 by Aloesci]