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Thread: Combining Hydrogen with Oxygen

  1. #1 Combining Hydrogen with Oxygen 
    Forum Senior miomaz's Avatar
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    hi,
    what happenes while combining Hydrogen with Oxygen in a enclosed metal box, if the box is filled to 2/3 of Hydrogen and 1/3 of Oxygen?
    I know that it reacts to water, but does this create a kind of vacuum in the box? If yes, how much and how much water is in the box after the reaction? is there a limit to the vacuum that is created?


    thanks,

    Mark


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    First it would create an explosion, then if the box did not blow apart, it would cool and condense forming a vacuum. The weight of water would be equal to the weight of the hydrogen plus the oxygen originally contained in the box, i.e., not much. The pressure would be equal to the vapor pressure of water at whatever the final temperature is.


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  4. #3  
    Forum Senior miomaz's Avatar
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    First of all, thank you for the information, but I'm searching for how strong the explosion, how big is the difference (in size) between the mixture of Hydrogen and oxygen and its reaction to water?

    Sorry but I wanted to make sure that the numbers which believe to get sort of match with reality’s, before I test it myself. (Just to let you know why I need it this precise)
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    According to the Wikipedia article on hydrogen, 1 liter of hydrogen (1 mole/ gm H2) at 0C and atmospheric pressure weighs .08988 grams. If you burn that amount of hydrogen according to
    2 H2(g) + O2(g) → 2 H2O(l) + 572 kJ/mol
    you would get 572/2 *.08= 22.8 kilojoules. (I think)
    Which is 16 226 foot-lbs. A high powered rifle bullet has about 2000 foot-pounds of energy.

    Corrected. I was way off. Still its a lot of energy
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  6. #5  
    Forum Isotope Bunbury's Avatar
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    You could easily kill, burn or blind yourself or somebody else if you test this yourself. It is a very dangerous experiment.
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  7. #6  
    Forum Senior miomaz's Avatar
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    Thanks Harold, this helps me allot! The kilo joule unit is meant for the explosion, not the vacuum created, I suppose. I'll try to find this out - so you can have the (practical) numbers if you are interested.

    Referring to the last post: It is not at all dangerous. I built an apparatus today (three in fact) and the out come per hour at 9v & 15v is very little. About 10ml/h.
    When I ignited the gas-mixture it 'barked' and gave a pretty nice biting flame out of the bottle.
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    If we assume the contents of the box cools down to room temperature, 21 C and there is some liquid water condensed in the box, the water vapor will have a pressure of 0.0249 bar.
    http://www.efunda.com/materials/wate...mtable_sat.cfm
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  9. #8  
    Forum Isotope Bunbury's Avatar
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    Well miomaz, your original post referred to an enclosed metal container. If you saw a flame out of the bottle I must assume the metal container (bottle?) did not remain intact, or it had a closure (cap) that came off. This means some or most of the water produced was lost to the atmosphere, and of course you could not pull a vacuum if the container ruptured. The reference to outcome per hour suggests a continuous process, not an explosion. So I'm not quite sure what it is you're trying to demonstrate.

    In fact if you have a stoichiometric mixture in a closed container, the heat release on ignition will almost instantaneously cause a very large increase in temperature and it is this temperature increase that leads to a pressure increase (gas laws) that either will or will not rupture the container, depending on the geometry and strength of the container. Also depending on the metal's properties, the rupture could produce shrapnel that could take out your eye. If you believe this is not dangerous you are mistaken. The fact that your particular setup didn't do any damage might be due to your careful calculations of heat release, pressure rise, and material strength, but I am guessing it was in fact due to luck. Am I right?
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  10. #9  
    Forum Senior miomaz's Avatar
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    Bunbury, the amount of hydrogen oxygen mixture I am using is very small, since I am only experimenting I only use about 100ml gas at room temperature. The explosion is comparable to a few drops of gasoline, when ignited.
    Ofcourse it is dangerous if I would have a tank full of hydrogen gas and would be filling metal boxes with it to ignite (which would be alittle more than a small gasoline drop explosion). The expansion pressure will not be enough to rip appart the plastic bottle that I have used (with the lid opened.)

    The bottle was apre experiment before I go on to a cylinder. Where I will be using a cylinder of a motor which is able to withstand the pressures.

    regards,

    Mark
    I haven't come to fight my word, but to find the truth.
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  11. #10  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by miomaz
    The expansion pressure will not be enough to rip appart the plastic bottle that I have used (with the lid opened.)

    The bottle was apre experiment before I go on to a cylinder. Where I will be using a cylinder of a motor which is able to withstand the pressures.

    regards,

    Mark
    Oh dear.

    I hope you do not think that an opened plastic container, and its response to the H O reaction, is an analogue of the sort of thing that can/will happen in a sealed container (no matter how strong)?

    It's been a pleasure having you on this forum so far and I'd hate to have to lose you through your blindness or death or some such.

    A car engine cylinder is certainly designed to take a lot of stress - but usually with the 'escape valve' of a moving piston.

    Please be wary, Mark, and take Bunbury's warning seriously. You do not want to be the next candidate for the Darwin Awards. Or do you?

    cheer

    shanks
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  12. #11  
    Forum Sophomore Matt Lacey's Avatar
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    I've done the Hydrogen/Oxygen explosion experiment before and really would not recommend doing it unless you know what you're doing. It can be an interesting experiment to do if you have a proper explosion chamber and equipment that you can use to evacuate the chamber and control the flow of the gases. This way you can look at the explosion limits at low pressures, etc, and not risk blowing something up if you get it wrong.
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