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Seperating water into oxygen and hydrogen.

  1. Feb 29, 2004 #1
    I remember in 8th grade I was sick the day my class did this, and no one I talk to seems to remember how it was done beyond there was a 9volt battery involved. Does anyone know how water can be seperated into hydrogen and oxygen?
  2. jcsd
  3. Feb 29, 2004 #2


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    The battery is attached to two metal rods (each wired to one battery terminal) placed in the water (not too near each other). A small amount of some salt or similar material (baking soda) may be needed, unless your water is hard (high in mineral content).
  4. Mar 1, 2004 #3


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    Why must the electrodes by "far away?" Why must the water contain impurities?
  5. Mar 1, 2004 #4
    Impurities are needed so the water contains more ions in solution which are neccessary for a current to flow. Water *does* conduct by itself in a pure form but very badly as the equlibrium of H20 <--> OH- + H+ lies heavily on the left hand side (pKa = 16). i.e. OH- very unstable conjugate base.
  6. Mar 1, 2004 #5


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    But won't the impurities corrupt the electrodes? The electrodes can't discriminate between a H+ and a Na+, can they? I'm still not seeing the added benefit of impurities.

    And, what about the separation of the electrodes? Anyone have an explanation for that?
  7. Mar 1, 2004 #6
    How would I go about collecting the Hydrogen and Oygen gases? Would I turn 2 test tubes upside down and fill them with water and put one of the metal metal rods in each test tubes? If I did that, would I have a combination of oxygen and hydrogen gas in each test tube, or would one have hydrogenand one oxygen?
  8. Mar 1, 2004 #7


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    You could use a u shaped container with one rod in each arm of the u. Of course, you need to cap the tops of the two arms to prevent the gasses from escaping. Hydrogen will collect in one arm and Oxygen in the other. The ions from the salts will react with the water, so don't worry about them. Also you don't need much, just so that the water will conduct the electricity. Pure water is a very poor conductor.
  9. Mar 1, 2004 #8
  10. Mar 1, 2004 #9


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    Use separate tubes for the gases. H will collect in one O in the other. No need to add any impurities most water has plenty, in addition the metals will contribute Ions for current flow. Seems to me that zinc was a good metal for one electrode.
  11. Apr 22, 2004 #10
    The actual action taking place in this process is that the carbon rods used to transmit the electricity from the 12 volt battery is actually themselves being broke down into the water as well so the resulting gas is actually a combination of hydrogen, oxygen, carbon, and a few others from impurities. The gas you would gather would be highly flamable but definitely not just hydrogen or oxygen or even just both.

    (how to do it)
    I'd type it out but this link is much more detailed and informative.


    Provides an efficient enough of a gas to power a 5hp generator.
  12. Nov 19, 2007 #11
    So what im not understanding is how do you make water into hydrogen? I know you are all thinking wow shes stupid but i really don't understand science. :confused: I also have a science project due here in a couple of weeks but i just don't get it and my teacher is nnot at all a help she just yells at me and gets all mad! So please someone help me!!!!!

  13. Nov 19, 2007 #12


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    The method described in the thread so far is basically telling you how to do just that. Maybe it will help to change the way you look at it. You see, it's not so much a matter of "turning water into hydrogen," the hydrogen is already in the water, because water is 2 parts hydrogen and one part oxygen. All you're doing is seperating the two. So you'll get hydrogen on one electrode, and oxygen on the other, although I can never remember which is which. Just please be very careful not to let a spark near this experiment.

    I wouldn't even try this one without parental supervision; and I'm over 40!
  14. Nov 20, 2007 #13
    God i love you and I don't even know you!!! lol jkjk
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