Asked by Matt

For the following electrochemical cell:
Fe(s)/Fe2+(aq)//MnO4–(aq), Mn2+(aq)/ Pt(s)

Which letter corresponds to the correct balanced chemical equation in an acidic solution?


A. 2Mn2+(aq) + 8H2O(l) + 5Fe2+ ==> (aq)5Fe(s) + 16H+(aq) + 2MnO4–(aq)
B. 5Fe(s) + 16H+(aq) + 2MnO4–(aq)2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq)
C. Fe(s) + 8H+(aq) + MnO4–(aq) ==> Mn2+(aq) + 4H2O(l) + Fe2+(aq)
D. Fe(s)+8H+(aq)+MnO4–(aq)+Pt2+(aq)==> Mn2+(aq)+4H2O(l)+Fe2+(aq)+Pt(s)
E. Mn2+(aq)+4H2O(l)+Fe2+(aq)+Pt(s) ==>Fe(s)+8H+(aq)+MnO4–(aq)+Pt2+(aq)

What reaction is occurring at the cathode?


A. 5e– + 8H+(aq)+MnO4–(aq)==>Mn2+(aq) +4H2O(l)
B. Fe2+(aq) + 2e– ==> Fe(s)
C. Fe(s)==>Fe2+(aq) + 2e–
D. Mn2+(aq) + 4H2O(l)==>5e– + 8H+(aq) + MnO4–(aq)
E. Pt(s)==>Pt2+ + 2e
Answered by DrBob222
What do you think and why?
#2. Reduction occurs at the cathode (the + charged electrode).
Answered by Matt
#1, Fe(s) is on the left, so it's anode; Pt(s) is on the right, it's a cathode...so the rxn should be D.

#2: B because Fe is gaining electrons, making it a reduction=cathode.
Answered by DrBob222
Right on the anode and cathode. If D is the correct answer, why doesn't it have Fe in it. There's no Fe in D. And you need an Fe going to Fe^+2 + 2e.
Answered by Matt
no, there's Fe in D for the first question..Fe(s)+8H+(aq)+MnO4–(aq)+Pt2+(aq)==> Mn2+(aq)+4H2O(l)+Fe2+(aq)+Pt(s)
Answered by DrBob222
You're right and I'm wrong. I was looking at the second set of answers and not the first. So Fe is on the left and it is the anode. So now what reaction is occurring at the Pt electrode? Obviously it's the other half cell, which is______?
Answered by Matt
Pt is functioning as a cathode
- D shows that Pt is cathode and Fe as anode. I don't understand why H+ and water are in the reaction

so my answers
1)D
2)B
Answered by DrBob222
D is correct for #1. For #2, isn't the correct answer A? Pt is the cathode (+ electrode where reduction occurs) and that is the MnO4^- reaction going to Mn^+2.
Answered by RoRo
the answer is actually B and A
Answered by yi
isn't Pt just functioning as an electrode?
Answered by UCI Student
answer is B and A
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