[xshadow]

HII!!

Have to balance this redox:

FeS₂ + Na₂O₂  -->  Na₂SO₄ + Na₂O + Na₂FeO₄

First I balanced the Sulfur atom:
FeS₂ + Na₂O₂  --> 2 Na₂SO₄ + Na₂O + Na₂FeO₄
FeS₂ + Na₂O₂  --> 2 Na₂SO₄ + Na₂O + Na₂FeO₄

OX1:  2S (-1)  ---> 2S (VII)  + 14 e-
OX2:  Fe(II) ---> Fe (VI) + 4 e-

OX TOT: 18e-

Now I have trouble with the oxygen/ reduction
Because on the left I have  Na₂O₂ with N.O = -1.
On the right I have three oxygen with  N.O= -3 and I don't know how to advance.

If I consider only Na₂O on the right  I get:
FeS₂ + Na₂O₂  --> 2 Na₂SO₄ + 2Na₂O + Na₂FeO₄    (balanced the oxygen involved in the redox as i done before with Sulfur)

2O (-1) + 2e- --> 2O (-2)

OX TOT : 18 e-   X1
RID: 2 e-           X9


FeS₂ + 9Na₂O₂  --> 2 Na₂SO₄ + 18Na₂O + Na₂FeO₄

But doens't work.
Thanks

[Borek]

OX1:  2S (-1)  ---> 2S (VII)  + 14 e-

S(VI), but I suppose that's just a typo, as electrons are OK.

On the right I have three oxygen with  N.O= -3

Another typo?

If I consider only Na₂O on the right  I get:
FeS₂ + Na₂O₂  --> 2 Na₂SO₄ + 2Na₂O + Na₂FeO₄  (balanced the oxygen involved in the redox as i done before with Sulfur)

Not sure what you did here nor why. Oxygen is not balanced.

This is actually easier to balance just by inspection, start with a single FeS₂ and see where it leads you.