Textbook Question
Complete and balance the following half-reactions in acidic solution. In each case indicate whether the half-reaction is an oxidation or a reduction. b. H2SO3(𝑎𝑞)⟶SO42−(𝑎𝑞)
6. Chemical Quantities & Aqueous Reactions
Balancing Redox Reactions: Acidic Solutions
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What is the balanced equation for the redox reaction occurring in acidic solution: Au3+(aq) + Cr3+(aq) → Au(s) + Cr2O7^2-(aq)?
A
2 Au3+(aq) + 3 Cr3+(aq) + 7 H2O(l) → 2 Au(s) + Cr2O7^2-(aq) + 14 H+(aq)
B
4 Au3+(aq) + Cr3+(aq) + 7 H2O(l) → 4 Au(s) + Cr2O7^2-(aq) + 14 H+(aq)
C
6 Au3+(aq) + 2 Cr3+(aq) + 7 H2O(l) → 6 Au(s) + Cr2O7^2-(aq) + 14 H+(aq)
D
3 Au3+(aq) + 2 Cr3+(aq) + 7 H2O(l) → 3 Au(s) + Cr2O7^2-(aq) + 14 H+(aq)
Verified step by step guidance1
Identify the oxidation and reduction half-reactions. In this case, Au3+ is reduced to Au, and Cr3+ is oxidized to Cr2O7^2-.
Write the reduction half-reaction: Au3+(aq) + 3 e^- → Au(s). This shows the gain of electrons by gold ions.
Write the oxidation half-reaction: 2 Cr3+(aq) + 7 H2O(l) → Cr2O7^2-(aq) + 14 H+(aq) + 6 e^-. This shows the loss of electrons by chromium ions.
Balance the electrons between the two half-reactions. Multiply the reduction half-reaction by 2 and the oxidation half-reaction by 1 to balance the electrons exchanged.
Combine the balanced half-reactions to form the overall balanced equation: 6 Au3+(aq) + 2 Cr3+(aq) + 7 H2O(l) → 6 Au(s) + Cr2O7^2-(aq) + 14 H+(aq).
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