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Hydrogen from water

  1. Oct 16, 2005 #1
    last night i tried to get hydrogen from water using the aparatus shown.
    i have to improve my collection tecnique but i was able to collect about a third of a cup ful ..
    say i collect it from the top of a dome shape device .
    my question is how will i mix it with the oxygen , to burn it

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  2. jcsd
  3. Oct 16, 2005 #2
    second pic.

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  4. Oct 16, 2005 #3


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    I can't really tell what I'm looking at there, but if you are doing electrolysis, you are getting oxygen. Since water has both hydrogen and oxygen, splitting it up liberates both (one at the cathode, one at the anode).
  5. Oct 16, 2005 #4
    Thanks for the reply ,
    iwas wondering wether or not the gas would be mixed , or would it be mostly hydrogen at the top , of the collector?
  6. Oct 16, 2005 #5


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    The hydrogen bubbles up from the cathode and oxygen at the anode. The cathode is negatively charged (connected to the minus side of the battery) and the anode is positively charged (connected to the positive side of the battery).

    Examine your apparatus and determine which is the anode and which is the cathode. The bubbles that form on those plates are as described above. If those bubbles mix above the water, then you'll have a mixture of oxygen and hydrogen. If you separate them, you will have hydrogen on the one side and oxygen on the other.

    Hope that helps.
  7. Oct 16, 2005 #6
    In its current configuration , i was putting 4.09 V at 2 A into the device..
    which is a calculated 2 Ohms ( approx)..
    it actually started bubbling at less voltage and current..
    thanks for the reply
    Edit : pic 2 ; Is a set of 12 plates alternating copper and zinc , seperated by little pieces of insulators .. top front is the solder connection to the zinc plates ( zinc coated steel)..
    bottom front is the connection to the copper plates..
    that loop of wire in the very front is just a handle and has no electrical connections
    Last edited: Oct 16, 2005
  8. Oct 17, 2005 #7
    Ok i've improved the collecter
    That H2 , O2 Flame is colorless isnt it ??
    It lights with a little pop ..
    I wasnt sure it was lit , till i burnt my finger with it..:bugeye: :wink:

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  9. Nov 16, 2005 #8
    [tex]2H_{2}O \Rightarrow H_2 + 2O_2[/tex]
    For safe storage of [itex]H_2[/itex] you might want to collect it seperately from the [itex]O_2[/itex].
    Any special reason why you used dissimilar metal electrodes, like you would in a voltaic cell?
    Last edited: Nov 16, 2005
  10. Nov 16, 2005 #9


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    Generally you do that so you don't destroy your electrodes. For the cathode (negative), it really doesn't matter what you use because that one stays together. For the anode it makes a huge difference. You're supplying a positive voltage (pull electrons) to a metal, and metals tend to dissolve when they lose electrons. That blue scum in your water is copper (2) something; it's coming from your self destructing copper anode.

    Get a carbon anode.
    Last edited: Nov 16, 2005
  11. Nov 17, 2005 #10
    That's interesting, they never told me in class. Next week I'm doing an electrolysis of copper(II) sulfate, and we're allowed to choose electrodes by ourselves. I should keep that in mind.

    Other than that, the cathode material doesn't really affect much, especially electroplating rate-wise?
  12. Nov 17, 2005 #11


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    Generally speaking, your cathode should be more inert than the dissolved metal. For example, you can plate chromium or aluminum onto iron, or iron onto copper, or copper onto platinum, but you cannot plate copper onto iron, or iron onto aluminum. Maybe you can, but I haven't found a way to do it.
  13. Nov 18, 2005 #12
    Has anyone tried electrolysing a mixture of copper(II) sulphate and zinc(II) sulphate? Will that result in a layer of brass on the cathode, or will it somehow act up?
  14. Nov 18, 2005 #13


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    Brass will not form. Copper that plates onto the cathode will stay there. Zinc that plates onto the cathode will be destroyed by any copper ions in solution; fine chunks of copper will fall to the bottom and zinc will dissolve again.
  15. Jan 12, 2006 #14
    I have heard that pulsating DC results in electrolysis taking place more rapidly. I tend to think this doesn't make much sense. Does anyone know about the effects of constant input voltage versus pulsating DC on the electrolysis process?
  16. Jan 12, 2006 #15


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    I've never heard of pulsing DC for electrolysis, but it does bring a different question to mind. If you start with very slow AC, say 1/5Hz, you'd have alternately hydrogen and then oxygen forming on each electrode every 5 seconds. What would happen as you increase the frequency? Is there a point where the molecules just wouldn't separate any longer?
  17. Jan 12, 2006 #16
    Good question... I was wondering about the effects of AC as well...
  18. Jan 12, 2006 #17


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    Short answer? Yes.

    Longer answer takes more space than post limits allow. If you're curious, do some reading on "electrolyte conductance/conductivity" measurement methods, measurement of dielectric constants, frequency dependence of dielectric constant, Walden product, and that's enough for now. There will be a quiz tomorrow.
  19. Mar 3, 2006 #18
    What is the best readily available power supply to use to make hydrogen? Taking in mind i don't want to be working with dangerous amounts of current. Another thing is I dont want to short circuit any thing expensive. I was thinking of using a car battery charger; you just plug it into the wall and put the croc clips onto your electrodes. Can anybody give me any reccomendations?
  20. Apr 22, 2006 #19
    This is my first time at this forum, so I don't know if anyone knows of this site. I have been exp. with hydrogen gen. using pulsating dc. It seems to work fairly well. I'm not sure what the rules are on posting web links, but I would be happy to share the link with anyone intrested.
  21. Apr 24, 2006 #20


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    Actually I have tried doing that. The result: it destroyed the battery charger.
    I saturated the solution with table salt to make sure it had good conductivity. When I connected the battery charger, the gauge said about 4 amps was going through the cell, and bubbles were coming off the electrodes like crazy (I was trying to plate metal, not make hydrogen). I thought that was going good so I left and went shopping. I came back a few hours later to check on my cell and things were not good. To start, the entire garage had a very strong smell to it; it had that smell like when you pour hydrochloric acid on aluminum foil. I think that's the smell of hydrogen but I can't be sure. Secondly, the gauge said there was now 10 amps flowing through the cell; the solution must have made acid or something since hydrogen is one of the few things that would increase conductivity that much. Due to the high current, the solution was literally boiling hot. A few days later, the gator clips for the battery charger were completely rusted, and even after polishing the connectors I could not get a measurable current to flow between the electrodes.

    I think the problem was caused by the voltage simply being too high. Electrolysis should be something like 1 volt, but a battery charger is >12 volts (the battery you are charging is rated for 12). On top of that the current was way too high at 4 amps. Even 1 amp is pretty damn high, but this again is caused by the voltage being too high (ohm's law).

    If I were to do it again I would probably use a bunch of D size batteries hooked in parallel. That would give 1.5 volts with some pretty high current.
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