Multiple Choice
In a galvanic cell operating in an acidic solution, which of the following represents the correct half-reaction occurring at the anode?
6. Chemical Quantities & Aqueous Reactions
Balancing Redox Reactions: Acidic Solutions
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What is the balanced half-reaction for Al(s) + MnO4^-(aq) -> Al^3+(aq) + Mn^2+(aq) in acidic conditions?
A
Al(s) + 4H2O(l) + MnO4^-(aq) + 8H^+(aq) -> Al^3+(aq) + Mn^2+(aq) + 4H2O(l)
B
Al(s) + 3H2O(l) + MnO4^-(aq) -> Al^3+(aq) + Mn^2+(aq) + 3OH^-(aq)
C
Al(s) + 2H2O(l) + MnO4^-(aq) + 4H^+(aq) -> Al^3+(aq) + Mn^2+(aq) + 2H2O(l)
D
Al(s) + 4H2O(l) + MnO4^-(aq) -> Al^3+(aq) + Mn^2+(aq) + 4OH^-(aq)
Verified step by step guidance1
Identify the oxidation and reduction components in the reaction. Aluminum (Al) is oxidized to Al³⁺, and permanganate ion (MnO₄⁻) is reduced to Mn²⁺.
Write the oxidation half-reaction for aluminum: Al(s) → Al³⁺(aq) + 3e⁻. This shows aluminum losing three electrons.
Write the reduction half-reaction for permanganate: MnO₄⁻(aq) + 8H⁺(aq) + 5e⁻ → Mn²⁺(aq) + 4H₂O(l). This shows permanganate gaining five electrons in acidic conditions.
Balance the electrons between the oxidation and reduction half-reactions. Multiply the oxidation half-reaction by 5 and the reduction half-reaction by 3 to balance the electrons exchanged.
Combine the balanced half-reactions, ensuring that the electrons cancel out, and verify that all atoms and charges are balanced in the final equation.
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