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. Fe(s) + 8H+(aq) + MnO4–(aq)Mn2+(aq) + 4H2O(l) + Fe2+(aq)
B. 5Fe(s) + 16H+(aq) + 2MnO4–(aq)2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq)
C. Fe(s)+8H+(aq)+MnO4–(aq)+Pt2+(aq)Mn2+(aq)+4H2O(l)+Fe2+(aq)+Pt(s)
D. 2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq)5Fe(s) + 16H+(aq) + 2MnO4–(aq)
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. Mn2+(aq) + 4H2O(l)5e– + 8H+(aq) + MnO4–(aq)
B. Fe(s)Fe2+(aq) + 2e–
C. Fe2+(aq) + 2e–Fe(s)
D. 5e– + 8H+(aq)+MnO4–(aq)Mn2+(aq) +4H2O(l)
E. Pt(s)Pt2+ + 2e–
B and D
To determine the correct balanced equation in an acidic solution, we need to analyze the given choices and identify the one that has the same number of each type of atom on both sides of the equation.
Let's look at each option one by one:
A. Fe(s) + 8H+(aq) + MnO4–(aq) -> Mn2+(aq) + 4H2O(l) + Fe2+(aq)
B. 5Fe(s) + 16H+(aq) + 2MnO4–(aq) -> 2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq)
C. Fe(s) + 8H+(aq) + MnO4–(aq) + Pt2+(aq) -> Mn2+(aq) + 4H2O(l) + Fe2+(aq) + Pt(s)
D. 2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq) -> 5Fe(s) + 16H+(aq) + 2MnO4–(aq)
E. Mn2+(aq) + 4H2O(l) + Fe2+(aq) + Pt(s) -> Fe(s) + 8H+(aq) + MnO4–(aq) + Pt2+(aq)
Now, let's count the number of atoms on both sides and see which option is balanced:
A. Fe: 1 on both sides, H: 8 on both sides, Mn: 1 on both sides, O: 4 on both sides -> balanced
B. Fe: 5 on both sides, H: 16 on both sides, Mn: 2 on both sides, O: 8 on both sides -> balanced
C. Fe: 1 on both sides, H: 8 on both sides, Mn: 1 on both sides, O: 4 on both sides -> balanced
D. Fe: 10 on both sides, H: 16 on both sides, Mn: 2 on both sides, O: 8 on both sides -> balanced
E. Fe: 1 on both sides, H: 8 on both sides, Mn: 1 on both sides, O: 4 on both sides -> balanced
From this analysis, we can see that all the options are balanced equations. Therefore, we need to consider the given question about the reaction occurring at the cathode to determine the correct option.
Looking at the options, the reaction at the cathode involves the gain of electrons, which is reduction. The correct answer would be the one that shows the reduction half-reaction at the cathode.
Let's analyze the options for the reaction at the cathode:
A. Mn2+(aq) + 4H2O(l) + 5e– -> 8H+(aq) + MnO4–(aq)
B. Fe(s) -> Fe2+(aq) + 2e–
C. Fe2+(aq) + 2e– -> Fe(s)
D. Not a reduction half-reaction (oxidation reaction)
E. Pt(s) -> Pt2+ + 2e–
From this analysis, we can see that option C correctly represents the reduction half-reaction at the cathode:
Fe2+(aq) + 2e– -> Fe(s)
Therefore, the correct answers are:
1. The balanced equation in an acidic solution is option C: Fe(s) + 8H+(aq) + MnO4–(aq) + Pt2+(aq) -> Mn2+(aq) + 4H2O(l) + Fe2+(aq) + Pt(s)
2. The reaction occurring at the cathode is option C: Fe2+(aq) + 2e– -> Fe(s)