enter image description here Hello, I am bit confused about balancing these type of redox reactions where multiple elements are involved in oxidation and reduction reactions.

If I try to use half reaction ion exchange method and write reduction and oxidation half separately and then try to neutralise the electrons then I am not able to go to RIGHT solution of this particular reaction.

Is there any simple way?

  • $\begingroup$ Although, i got right answer but not by typical process, i got it by combining ion electron method by elemental level balancing with hit and trial approach... I want to know, if there is any predefined way to do so? $\endgroup$ Jun 1 '18 at 11:07
  • $\begingroup$ If what you show in the picture is supposed to be the final balanced equation, it isn't correct. If that's not the final answer, perhaps you should show what you have as the correctly balanced equation. $\endgroup$
    – Dr. J.
    Jun 1 '18 at 11:39
  • $\begingroup$ That isn't a final balanced equation, it is my effort which is wrong. $\endgroup$ Jun 1 '18 at 11:40

Here is an easy way to balance this.
Balance in order: (1) metals; (2)ions; (3) non metals; (4) oxygen
FeS2 + O2 ==> Fe2O3 + SO2
Balance metals (Fe)
2FeS2 + O2 ==> Fe2O3 + SO2
There are no ions, so balance non metals next (S)
2FeS2 + O2 ==> Fe2O3 + 4SO2
Finally balance O
2FeS2 + 5.5 O2 ==> Fe2O3 + 4SO2 (and multiply through by 2 to get)
4FeS2 + 11O2 ==> 2Fe2O3 + 8SO2


Write the components in their dissociated (ionic) forms, such as Fe2+ + S22- Then write sub reactions, or more properly actual redox reactions. Here 1 for Fe(II) oxidation to Fe(III) by oxygen, and disulfide ion oxidation to sulfur dioxide by again oxygen. Solve these two reactions separately then combine reactants and products in the last step. That is the simple and safe way.

  • $\begingroup$ Tried, but didn't got it balanced & right :( $\endgroup$ Jun 1 '18 at 12:00
  • $\begingroup$ "Aquatic" is the wrong word here. Other than that, the method should work. $\endgroup$ Jun 1 '18 at 12:02
  • 1
    $\begingroup$ It says "disulfide ion oxidation to sulfate", but I don't see any sulfate anion. How can this method work? $\endgroup$
    – Dr. J.
    Jun 1 '18 at 20:11
  • $\begingroup$ Take the sulphur dioxide instead of sulfate. I just had a mistake there. And I also inclined to take this reaction in solution, I am working on them for a long time, but it does not have to be so. Rather than aquatic, dissociated forms are more appropriate I guess. $\endgroup$ Jun 5 '18 at 8:21

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