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WHAT HAPPENS IF I HEAT Fe2+ or Mn2+ in air?

  1. Jul 28, 2011 #1
    I am wondering if I heat Fe2+ Or Mn2+ in air at 700 to 1000 C, does their oxidation number change??? if yes, how should I avoid this, when heating in a furnace???

    Thanks in advance
     
  2. jcsd
  3. Jul 28, 2011 #2

    uby

    User Avatar

    i assume you mean if heating FeO in air will further oxidize it to Fe2O3? YES it will.

    thermodynamics will provide the equilibrium oxygen partial pressure:
    2Fe2O3 = 4FeO + O2(g)
    K_rxn = pO2 / p_total

    one method to pin oxygen partial pressure is to flow an inert gas through a mixture of Fe2O3 and FeO powders, which can set the oxygen partial pressure flowing over your sample. just ensure you have a large excess of powder relative to the number of moles of oxygen that might need to be absorbed or released, and that the powders are held at a temperature where the reaction kinetics are fast (but not so high that the powders sinter and coarsen, else you lose surface area and decrease kinetics)
     
  4. Jul 28, 2011 #3
    Thanks :)

    What about CrCl3 ??? will the oxidation number of Cr3+ change under when heating in air at 1000C?
     
  5. Jul 28, 2011 #4

    uby

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    i think you should be worried about other reactions when heating halides in air.

    e.g., sublimation/evaporation CrCl3 = CrCl3(g)
    oxidation 4CrCl3 + 3O2(g) = 2Cr2O3 + 6Cl2(g)
    etc.
     
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