Multiple Choice
Balance the following redox reaction in basic solution: MnO4- (aq) + Br- (aq) → BrO3- (aq) + MnO2 (s). What is the coefficient in front of H2O in the balanced reaction?
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6. Chemical Quantities & Aqueous Reactions
Balancing Redox Reactions: Basic Solutions
Multiple Choice
Which of the following is the correctly balanced equation for the oxidation reaction of Cr2O7^2-(aq) and C2O4^2-(aq) in a basic solution using the half-reaction method?
A
Cr2O7^2-(aq) + C2O4^2-(aq) + 4OH^-(aq) -> 2Cr^3+(aq) + 2CO2(g) + 2H2O(l)
B
Cr2O7^2-(aq) + 2C2O4^2-(aq) + 6OH^-(aq) -> 2Cr^3+(aq) + 4CO2(g) + 3H2O(l)
C
Cr2O7^2-(aq) + 3C2O4^2-(aq) + 8OH^-(aq) -> 2Cr^3+(aq) + 6CO2(g) + 4H2O(l)
D
Cr2O7^2-(aq) + 4C2O4^2-(aq) + 10OH^-(aq) -> 2Cr^3+(aq) + 8CO2(g) + 5H2O(l)
Verified step by step guidance1
Identify the half-reactions involved in the oxidation and reduction processes. For this reaction, the reduction half-reaction involves Cr2O7^2- being reduced to Cr^3+, and the oxidation half-reaction involves C2O4^2- being oxidized to CO2.
Balance the atoms other than O and H in each half-reaction. For the reduction half-reaction, balance the Cr atoms: Cr2O7^2- -> 2Cr^3+. For the oxidation half-reaction, balance the C atoms: C2O4^2- -> 2CO2.
Balance the oxygen atoms by adding H2O molecules. In the reduction half-reaction, add 7 H2O to the right side: Cr2O7^2- -> 2Cr^3+ + 7H2O. In the oxidation half-reaction, the oxygen atoms are already balanced.
Balance the hydrogen atoms by adding OH^- ions. In the reduction half-reaction, add 14 OH^- to the left side: Cr2O7^2- + 14OH^- -> 2Cr^3+ + 7H2O. In the oxidation half-reaction, add 4 OH^- to the right side: C2O4^2- + 4OH^- -> 2CO2 + 2H2O.
Combine the balanced half-reactions, ensuring that the electrons lost in the oxidation half-reaction equal the electrons gained in the reduction half-reaction. Adjust coefficients as necessary to achieve this balance, and simplify the equation by canceling out common species on both sides.
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