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Rusting of Magnesium

  1. Aug 30, 2004 #1
    Hi I was wondering what would be the equation for the rusting of magnesium?

    I did an experiment where an iron nail was covered by a strip of magnesium and was put into diluted NaOCl (diluted sodium hypochlorite solution). Apparently the magnesium protects the iron from rusting and hence rusts instead.



    Thanks,

    Tanya
     
    Last edited: Aug 30, 2004
  2. jcsd
  3. Aug 30, 2004 #2
    reply from HONG KONG CHEM LOVER

    Hi I was wondering what would be the equation for the rusting of magnesium?

    I did an experiment where an iron nail was covered by a strip of magnesium and was put into diluted NaOCl (diluted sodium hypochlorite solution). Apparently the magnesium protects the iron from rusting and hence rusts instead.

    1st: NaOCl+ H2O <>(reversible) NaCl + 2OH-
    2nd: Mg + 2OH->MgO (rust) +H2O
    is it right, i am not sure
     
  4. Aug 30, 2004 #3

    chem_tr

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    Science Advisor
    Gold Member

    Hello

    I am not sure the equations in the first reply is totally correct, the products are okay though; hypochlorite has 1+ valence on chlorine, but chloride consists 1- valence. So there has to be a redox chemistry, and therefore, a reduction step. The electrons must have released from magnesium atom, so magnesium atom must undergo an oxidation step. Let me summarize these below:

    Mg ---> Mg2+ + 2e-
    NaClO + 2e- + H2O ---> NaCl + 2OH-

    Mg + NaClO + H2O---> Mg(OH)2 + NaCl

    But magnesium oxide may also be produced if the temperature of the medium is sufficiently high to cause dehydratation (water removal):

    Mg(OH)2 ---> MgO + H2O

    PS: Please note that this approach is the ideal one; you may also predict that mixed products like Mg(OH)Cl and MgCl2 are likely to occur, but with a limited probablity. Therefore, sodium hydroxide is another possible side product.

    Regards
    chem_tr
     
    Last edited: Aug 30, 2004
  5. Aug 30, 2004 #4
    YES~ mine one is incorrect..

    sorry, i hve overlooked the Cl in OCl is +1
     
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