Question

How do we represent the formation of `Fe_3O_4` by the oxidation of iron metal in basic conditions?

Answer 1

`3Fe(s) +8H_2Orarr Fe^(2+) + 2Fe^(3+)+4H_2(g) +8HO^-`

Explanation:

If you got `Fe_3O_4`, this is mixed valence oxide of iron ......it occurs as the mineral magnetite, which we could formulate as `FeO*Fe_2O_3-=Fe_3O_4`.......

And so metallic iron is oxidized to `Fe^(2+) + 2xxFe^(3+)`............

`3Fe(s) rarr Fe^(2+) + 2Fe^(3+)+8e^(-)` `(i)`

But something must be correspondingly reduced.....and here it is the protium ion in water........

`H_2O+e^(-) rarr1/2H_2(g) + HO^-` `(ii)`

And so I take `(i)+8xx(ii)` to gives...........

`3Fe(s) +8H_2Orarr Fe^(2+) + 2Fe^(3+)+4H_2(g) +8HO^-`

Charge and mass are balanced as is required...........