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. Fe(s)+8H+(aq)+MnO4–(aq)+Pt2+(aq)-> Mn2+(aq)+4H2O(l)+Fe2+(aq)+Pt(s)
C. 5Fe(s) + 16H+(aq) + 2MnO4–(aq)-> 2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq)
D. Fe(s) + 8H+(aq) + MnO4–(aq)-> Mn2+(aq) + 4H2O(l) + Fe2+(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. Fe2+(aq) + 2e– -> Fe(s)
C. Fe(s)-> Fe2+(aq) + 2e–
D. 5e– + 8H+(aq)+MnO4–(aq)-> Mn2+(aq) +4H2O(l)
E. Pt(s)-> Pt2+ + 2e–
I thought we did this before. Tell me what you think and why.
To identify the correct balanced chemical equation in an acidic solution for the given electrochemical cell, we need to analyze the cells' components and their respective reactions.
The given electrochemical cell is set up as follows:
An iron electrode (Fe(s)) is in contact with an iron(II) ion solution (Fe2+(aq)) through a salt bridge. On the other side, a platinum electrode (Pt(s)) is in contact with a solution containing permanganate ion (MnO4–(aq)) and manganese(II) ion (Mn2+(aq)).
Now, let's go through each option to determine which one represents the correctly balanced chemical equation in an acidic solution:
Option A: 2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq) -> 5Fe(s) + 16H+(aq) + 2MnO4–(aq)
This equation is unbalanced because the number of oxygens and hydrogens on each side of the reaction is not equal.
Option B: Fe(s) + 8H+(aq) + MnO4–(aq) + Pt2+(aq) -> Mn2+(aq) + 4H2O(l) + Fe2+(aq) + Pt(s)
This equation is correctly balanced in terms of the number of atoms and charge. It represents the correct balanced chemical equation in an acidic solution for the given electrochemical cell.
Option C: 5Fe(s) + 16H+(aq) + 2MnO4–(aq) -> 2Mn2+(aq) + 8H2O(l) + 5Fe2+(aq)
This equation is unbalanced because the number of oxygens and hydrogens on each side of the reaction is not equal.
Option D: Fe(s) + 8H+(aq) + MnO4–(aq) -> Mn2+(aq) + 4H2O(l) + Fe2+(aq)
This equation is unbalanced because the number of oxygens and hydrogens on each side of the reaction is not equal.
Option E: Mn2+(aq) + 4H2O(l) + Fe2+(aq) + Pt(s) -> Fe(s) + 8H+(aq) + MnO4–(aq) + Pt2+(aq)
This equation is unbalanced because the number of oxygens and hydrogens on each side of the reaction is not equal.
Therefore, the correct balanced chemical equation in an acidic solution is Option B:
Fe(s) + 8H+(aq) + MnO4–(aq) + Pt2+(aq) -> Mn2+(aq) + 4H2O(l) + Fe2+(aq) + Pt(s)
Moving on to the second question, which asks about the reaction occurring at the cathode:
The cathode is the electrode where reduction occurs. In this case, the cathode is the platinum electrode (Pt(s)). Looking at the balanced chemical equation from Option B, we can see that the reduction half-reaction happening at the cathode is:
Fe2+(aq) + 2e– -> Fe(s)
Therefore, the correct answer is option B:
Fe2+(aq) + 2e– -> Fe(s)