Identifying Oxidized/Reduced Elements and Agents in Redox Reaction

Steps:

• Fe oxidation state: +2 in Fe²⁺ to +3 in Fe³⁺, increases, so Fe oxidized.
• S oxidation state in S₂O₈²⁻: (8O × -2 = -16; total -2 charge, so 2S = +14; each S +7); in SO₄²⁻: +6, decreases, so S reduced.
• Oxidizing agent: species causing oxidation (reduced itself), S₂O₈²⁻ containing S.
• Reducing agent: species causing reduction (oxidized itself), Fe²⁺ containing Fe.

Why C is correct:

• Sulfur reduced (oxidation state +7 to +6), acts as oxidizing agent; iron oxidized (+2 to +3), acts as reducing agent, per redox definitions.

Why the others are wrong:

• A: Iron oxidized, not reduced; SO₄²⁻ is product, not agent.
• B: SO₄²⁻ not oxidizing agent (it's reduced product).
• D: Sulfur reduced, not reducing agent; iron oxidized, not oxidizing agent.

Final answer: C