Multiple Choice
In the reaction ZnO + C → Zn + CO, which element is oxidized?
6. Chemical Quantities & Aqueous Reactions
Redox Reactions
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Which of the following represents the cathode reaction in the corrosion of iron metal to aqueous iron(II)?
A
Fe²⁺ + 2e⁻ → Fe
B
2H₂O + 2e⁻ → H₂ + 2OH⁻
C
O₂ + 4H⁺ + 4e⁻ → 2H₂O
D
Fe → Fe²⁺ + 2e⁻
Verified step by step guidance1
Understand the context of the problem: Corrosion of iron involves electrochemical reactions where iron is oxidized and electrons are transferred to another species, typically oxygen in the presence of water.
Identify the cathode reaction: In electrochemical cells, the cathode is where reduction occurs. Look for the reaction where electrons are gained by a species.
Examine the given reactions: The reaction O₂ + 4H⁺ + 4e⁻ → 2H₂O involves oxygen gaining electrons, which is a reduction process, indicating it occurs at the cathode.
Compare with other reactions: The reaction Fe → Fe²⁺ + 2e⁻ is an oxidation process (loss of electrons), and Fe²⁺ + 2e⁻ → Fe is a reduction of iron ions, not related to the cathode in iron corrosion.
Conclude the cathode reaction: The correct cathode reaction in the corrosion of iron is the reduction of oxygen, O₂ + 4H⁺ + 4e⁻ → 2H₂O, as it involves the gain of electrons by oxygen.
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