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

[Panthera Leo]

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

 

[uby]

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)

 

[Panthera Leo]

Thanks :)

What about CrCl3 ? will the oxidation number of Cr3+ change under when heating in air at 1000C?

 

[uby]

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.