[itsme03]

i tried to balance the following equation:
O₂ + I^-  :rarrow:I₂

I got at as far as 2H₂O + O₂ + 4I^-  4OH^- + 2I₂

If this is correct, please tell me how to move on. If not, please let me know how to get the correct answer.
Thank you!

[Borek]

Write both half reactions.

http://www.chembuddy.com/?left=balancing-stoichiometry&right=half-reactions-method

[itsme03]

i did. i got
4e^- + 2H₂O + O₂  4OH^-

&

2I^-  I₂ + 2e^-

[Borek]

So now you have to combine them in such a way that electrons cancel out.

[itsme03]

i did and i ended up with the equation i first posted

[Borek]

Nope. The electrons didn't cancel out - you had 4 on the left, 2 on the right, when you simply add both reactions, you were left with two electrons on the left.

Check if multiplying second reaction by some small integer won't help.

[itsme03]

no i multiplied the second equation by 2 so i  got
4I^-  I₂ + 4e^-

so the equation became

4e^- + 2H₂O + O₂ + 4I^-  4OH^- + 2I₂ + 4e^-

[Borek]

That's OK, but as far as I remember that's not the original equation you have posted - in the original one charges were not balanced. Have you edited your first post?

[itsme03]

no i havent. but arent the charges equal? theyre both -4

[Borek]

Equation is balanced OK.