Electrochemistry Galvanic Cell Question - Come on you know you want to answer this. You totally do.?

Question

What is the overall cell reaction?

(A)	Zn^2+ + 2H2O --> Zn + H2O2 + 2H+

(B)	Zn + H2O2 + 2H+ ---> Zn^2+ + 2H2O

(C)	Zn + H2O2 + 2H+ + 4e- ---> Zn^2+ + 2H2O

(D)	Zn^2+ + H2O2 ---> Zn + H2O + ½ O2

I know what the correct answer is but I am clueless as to why its the correct answer.

I worked it out and circled choice (B) but the answer key said no, that's completely wrong.

If anyone is willing to give this problem a go and answer with a choice and MOST importantly and complete and detailed explanation as to the reasoning behind the answer I would be MOST appreciative.

Thank you guys for taking the time to do this.

Jan · Accepted Answer

it should be (B), because Etot = 2.54 V > 0
and spontaneous reaction...
***
(A) Etot = -1.02 V < 0
and not  spontaneous reaction
***
(C) as (B), but not balanced
***
edit: yes it's possible with (D), because:
4H2O => 2H2O2 + 4H^+ + 4e^-, E1=-1.76 V
O2 + 2H2O + 4e^- => 4OH^-, E2=0.4 V
*****so total****
2H2O + O2 => 2H2O2, E (1+2)= -1.36 V
H2O2 => H2O + 0.5O2, E rev = +1.36 V > 0

***
***
Zn^2+/Zn is red, E=-0.76 V
H2O2/O2 is ox, E=1.36 V
E(tot) = 0.6 V => 
(D) is a spontaneous reaction

? · Answer

Get this you guys....the answer key says it's (D)....where the hell does the oxygen come from?  I'm beginning to wonder if the answer key could possibly be (dare I say it)...wrong?  Is there anyway you guys can see it being (D)??  I simply can't :-/

I&#39;Mma Curazy Man · Answer

I don't know. I bullcrapped this on the AP exam.

Electrochemistry Galvanic Cell Question - Come on you know you want to answer this. You totally do.?

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