Exploding Hydrogen Balloons: Fireball Size and Necessity of Flame

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Discussion Overview

The discussion revolves around the comparison of fireball sizes resulting from the explosion of hydrogen balloons filled with either pure hydrogen gas or a hydrogen-oxygen mixture. Participants explore the necessity of a flame to initiate the reaction and the implications for combustion dynamics and entropy changes.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether the balloon filled with pure H2 would produce a larger fireball due to a higher concentration of hydrogen gas.
  • Another participant asserts that pure hydrogen will not explode or burn without oxygen, suggesting that the H2/O2 mixture in a 2:1 ratio is optimal for a rapid reaction throughout the volume.
  • A different viewpoint suggests that while the pure H2 balloon may take longer to combust completely, it could still create a larger fireball due to the greater amount of hydrogen available for burning.
  • Participants discuss the role of a flame in initiating the reaction, with one noting that a flame is a simple and effective method to start the reaction and allow oxygen to join in.
  • One participant raises a question about which balloon reaction results in a larger increase in entropy of the surroundings and whether the H2 balloon releases more heat than the H2/O2 balloon.

Areas of Agreement / Disagreement

Participants express differing views on which balloon would produce a larger fireball and the implications of the reaction dynamics. There is no consensus on the outcomes or the specifics of the combustion processes involved.

Contextual Notes

Participants mention various assumptions regarding the conditions under which the reactions occur, including the need for a flame to initiate combustion and the potential for other ignition sources. The discussion does not resolve the complexities of heat content or entropy changes associated with the different balloon reactions.

Who May Find This Useful

This discussion may be of interest to individuals exploring combustion chemistry, reaction dynamics, or those studying the properties of gases in explosive scenarios.

chemister
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If you were to explode two different balloons, one filled with H2 gas and another filled with a mixture of H2 and O2 gasses in a 2:1 volume ratio, which balloon would have a much larger fireball associated with it and why?
Also, why is it necessary to start the reaction with a flame?



Would the H2 balloon have the largest fireball because of its higher concentration of hydrogen gas?
I was thinking that starting the reaction with a flame heats things up creating a faster movement of molecules. The faster movement of molecules means a higher velocity for collision creating the explosion. Is this correct?
THANKYOU!
 
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Pure hydrogen will not explode nor burn without oxygen, so you will get only reaction on the surface. Mixture 1:2 has optimal proportions so the reaction will take place in whole volume almost instantly.

How it translates into fireball I have no idea.

Your answer for the second question sounds OK with me, unless you are asked at your PhD exam :)


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assumming both balloons had equal volumes of total gas, that would mean that the balloon containing pure H2 would (although take logner to compleatly combust), create a bigger fireball because the is more hydrogen to burn, bigger explosion, I don't think that the speed of reaction is all that noticible on a small of scale as a ballon, both seem pretty instantaneuos to the naked eye.

you need to start it off with a flame, since the both together won't react/combust by themselves, they might slowly combine to form water, but won't (necesarly, under normal conditions) explode by themselves, something must set it off.
You could set it off by another means, say a very hot heating element, but a flame is a very simple and effective way of both starting the reacting and breaking/melting the balloon to allow air (and oxygen) to join in on the reaction.
 
Which balloon reaction is going to result in the largest increase in entropy of the surroundings and why?

Does the H2 filled balloon give off a higher heat content than the H2/O2 balloon?
 

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