Can Helium Be Converted into Hydrogen?

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Discussion Overview

The discussion revolves around the possibility of converting helium measurements into hydrogen equivalents, particularly in the context of safety assessments for hydrogen-fueled vehicles. Participants explore the implications of using helium as a substitute for hydrogen in testing scenarios where direct use of hydrogen is not feasible due to its flammability.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the clarity of the original inquiry, suggesting that the question may be poorly defined or based on a misunderstanding of the concepts involved.
  • Another participant explains that to convert helium measurements in mg/kg to hydrogen equivalents, one could divide by two, referencing the difference in molar masses.
  • A participant points out that while gases occupy the same volume at the same conditions, the conversion should consider molar volume rather than volume per mass.
  • Concerns are raised about the dynamics of gas mixing, with a participant suggesting that the behavior of helium might serve as a reasonable model for hydrogen due to differences in density.
  • There is a suggestion that engineering expertise may provide additional insights into the behavior of gases in the context of leakage and pressure dynamics.

Areas of Agreement / Disagreement

Participants express differing views on the clarity and feasibility of the original question, with some providing mathematical approaches while others emphasize the need for a more nuanced understanding of gas behavior. The discussion remains unresolved regarding the best method for converting helium measurements to hydrogen equivalents.

Contextual Notes

Limitations include potential misunderstandings of gas properties, the need for clarity in the original question, and the complexities involved in gas dynamics under different conditions.

Loveandbeer
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Hi everyone,

I'm not much good at chemistry, but I'm in need of a bit of help for a project I'm doing.

My question is: is it possible to convert a volume of helium into a volume of hydrogen? I'm looking at measurements of percentage of helium in the air, and want to convert them to an equivalent for hydrogen.

Sorry if this is a stupid question, I really am bad at chemistry.

Thanks for any help you can give me!
 
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Could be it is not a stupid question, but it doesn't make much sense as worded. You know, it is not even wrong. I guess you are mixing several ideas and concepts trying to solve some not well defined question. Or the question is well defined, it is just that you are confused and your approach is off.

Please elaborate on the problem you are trying to solve. What kind of equivalence between hydrogen and helium are you looking for?

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Ok I'll give it another go. It is quite an abstract idea though as I don't even know where to start, I only went up to Chemistry GCSE so barely have a grasp on moles haha.

Basically I am looking into the safety of hydrogen fuelled vehicles. Long story short, the amount of hydrogen that leaks into the passenger compartment after an impact needs to be measured to make sure the amount isn't going above the lower flammability limits (4%).

But hydrogen is too flammable to use in a normal crash test, so it needs to be done with helium filling the tanks instead.

So my thinking is, there needs to be a helium sensor in the passenger compartment. It will give me a reading of the concentration of helium present (in ppm or maybe mg/kg) and once they give a reading, that reading needs to be converted into one for hydrogen.
 
If you have it in mg/kg just divide by two. Thats from simple comparison of molar masses.

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But isn't the volume of all gases the same... irrespective of mass?
 
Molar volume, not volume per mass. 1 mole of hydrogen has the same volume as 1 mole of oxygen, 2 g of hydrogen have the same volume as 32 g of oxygen.

Note that this simplified approach will work on ppm level, when the concentrations are much higher calculations can get a little bit more difficult. Still, mg/kg is a very good starting unit.

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methods
 
Just brainstorming - sure He is twice as dense as H2. But this is a problem of the leakage or injection under pressure of a light gas into a heavier one and wouldn't the dynamics of mixing depend mostly on the difference of densities between the light gas and the dense one (air more than 14 times as dense as hydrogen) so making the helium behaviour not a bad model for hydrogen behaviour?
However if so I imagine there is some engineering experience and practice around it so maybe an engineering thread might find someone who knows what he is talking about? :biggrin:
 

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