|MadSci Network: Chemistry|
Water electrolyses like this: 2H+ + 2e- ---> H2 2OH- ---> 2e- + H2O + (1/2)O2 2H2O ---> H2 + (1/2)O2 + H20. (sorry, but I don't know how to get subscripts and postscripts into e- mail.) A normal battery has a high enough voltage to make this happen, use a 12V one if you don't have much patience. As you can see from the equations, 2 electrons will produce one Hydrogen molecule. Faraday's first law of electrolysis states that the mass of a substance produced at an electrode is proportional to the electricity passed (measured in Coulombs, one electron having a charge of 1.6*10^-19 Coulombs). This can be seen from the fact that to produce one mole of Hydrogen, you need 2 moles of electrons. Current is Charge per second, so the higher the current, the quicker you will produce Hydrogen and Oxygen. As well as NaCl, anything ionic will undergo electrolysis (because electrolysis is the movement of ions towards electrodes). Try other metal compounds, such as Copper Sulphate - which will plate the cathode in copper. Anything with an electropotential above Hydrogen's (such as Cu 2+, and Ag+ ions) will be discharged at the cathode in preference to Hydrogen. Anything with an Electropotential more negative than 0.4V (the value for O2 + H2O + 4e- ---> 4OH-) will be discharged at the anode in preference to Oxygen.
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