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Thread: Question : energy of dissociation of water by electrolysis

  1. #1 Question : energy of dissociation of water by electrolysis 
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    Hi all and happy new year,

    I needed to know the electrical energy necessary to dissociate a mole of water by electrolysis. I googled a little and found distinct sources giving distinct results, such as :
    • it is the enthalpy of dissociation of water : 285 or 286 KJ per mole.
    • it is the Gibbs free energy required for electolysis : 237 KJ per mole.
    • Some other sources do a computation of the balance of energy and conclude 241 KJ per mole.
    Finally, I tried my "own" computation : you need 2 moles of electrons for 1 mole of water. So the electric charge necessary is 2 F (Faraday constant) = 192970 C.

    The standard potential of electrolysis of water is 1.23V, so the energy needed is 192970 * 1.23 = 237 KJ per mole.
    But Wiki also mentions that the "real observed threshold of electrolysis" is 1.48V ... that is 285 KJ per mole.

    I am drowning. Can somebody help me out of this electrolytic bath ?


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