[samta]

I have been looking around on the internet and my in my textbook but i have not been able to find any examples of reactions with more than 2 participants, and i am completely lost as to how to solve this (do i need more than 2 half-reactions?)

SO₂ (aq)  +  I₂ (aq)  +  2H₂O(l)    →   4H⁺ (aq)  +  SO₄^2- (aq)  +  2I^- (aq)

1) Use oxidation numbers to explain why this is a redox reaction
2) Find the half-reactions

All help, hints and examples are appreciated!

[ramboacid]

Try balancing without the H₂O and 4H⁺, focusing only on the SO₂/SO₄^2- and I₂/2I^- half reactions. The H₂O and H⁺ should come as a consequence of balancing those half reactions.

[Borek]

If you don't see it, assign oxidation numbers first - that will let you find out what is being oxidized (first half reaction) and what is being reduced (second half reaction).

No, you don't need more than 2 half reactions.

[samta]

Thanks for the replies.

To get from SO₂ to SO₄^2- I need 2O, but then i will also have 4H⁺, and the reaction will be unbalanced?

SO₂ (aq)  + 2H₂O (l)   -> SO₄^2- (aq)  + 2H⁺ (aq) 


I₂ (aq)  -> 2H⁺ (aq)  +  2I^- (aq)

[Borek]

Don't worry about balancing oxygen and hydrogen yet - first step is to find out what is being oxidized and what is being reduced.

Have you tried to assign oxidation numbers as I asked?