## 2013 Final #4

Michelle_Nguyen_3F
Posts: 40
Joined: Wed Sep 21, 2016 2:59 pm

### 2013 Final #4

Given $2Fe(s) + 2H_{2}O(l) + O_{2} \rightarrow 2Fe(OH)_{2} (s)$, how would we write the half reactions? Thank you!

Andrea Medina 1A
Posts: 13
Joined: Wed Sep 21, 2016 2:58 pm

### Re: 2013 Final #4

I have a similar question how would we know the moles of electrons if we are not given the charges and Fe is a transition metal?

Pauline Tze 3B
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### Re: 2013 Final #4

2Fe(s) + 2H2O --> 2Fe(OH)2(s) + 4e-
pay attention to the charge for Fe as Fe is oxidized from 0 to +2
O2 + 4e- ----> 2Fe(OH)2(s)
pay attention to the charge for O as O is reduced from 0 to -2

Posts: 23
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### Re: 2013 Final #4

Wait, How would that work? The reduction reaction isn't balanced (Fe on products but not in reactants). I also had trouble determining n for this question.

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### Re: 2013 Final #4

So we would calculate the electron number from the changes in charges seen in the corresponding half reactions?