Textbook Question
Complete and balance the following half-reactions in basic solution. In each case, indicate whether the half-reaction is an oxidation or a reduction. c. Cr(OH)3(𝑠)⟶CrO42−(𝑎𝑞)
6. Chemical Quantities & Aqueous Reactions
Balancing Redox Reactions: Basic Solutions
Multiple Choice
Which of the following is the correctly balanced redox reaction for MnO4⁻(aq) + Br⁻(aq) → MnO2(s) + BrO3⁻(aq) in a basic solution?
A
3 MnO4⁻(aq) + 3 Br⁻(aq) + 2 H2O(l) → 3 MnO2(s) + 3 BrO3⁻(aq) + 4 OH⁻(aq)
B
MnO4⁻(aq) + Br⁻(aq) + H2O(l) → MnO2(s) + BrO3⁻(aq) + OH⁻(aq)
C
2 MnO4⁻(aq) + 2 Br⁻(aq) + 2 H2O(l) → 2 MnO2(s) + 2 BrO3⁻(aq) + 4 OH⁻(aq)
D
2 MnO4⁻(aq) + 2 Br⁻(aq) + H2O(l) → 2 MnO2(s) + 2 BrO3⁻(aq) + 2 OH⁻(aq)
Verified step by step guidance1
Identify the oxidation and reduction half-reactions. MnO4⁻ is reduced to MnO2, and Br⁻ is oxidized to BrO3⁻.
Balance the atoms other than oxygen and hydrogen in each half-reaction. Mn and Br are already balanced.
Balance the oxygen atoms by adding H2O molecules. For MnO4⁻ to MnO2, add 2 H2O to the right side. For Br⁻ to BrO3⁻, add 3 H2O to the left side.
Balance the hydrogen atoms by adding OH⁻ ions. For MnO4⁻ to MnO2, add 4 OH⁻ to the left side. For Br⁻ to BrO3⁻, add 6 OH⁻ to the right side.
Combine the balanced half-reactions, ensuring that the electrons cancel out, and verify that the final equation is balanced in terms of atoms and charge.
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