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

1. Jul 28, 2011

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???

2. Jul 28, 2011

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)

3. Jul 28, 2011

Panthera Leo

Thanks :)

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

4. Jul 28, 2011

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.