Answer:
H⁺(aq)
Explanation:
Let's consider the following redox reaction.
Sn(s) + 2 H⁺(aq) → Sn²⁺(aq) + H₂(g)
We can identify both half-reactions.
Oxidation: Sn(s) → Sn²⁺(aq) + 2 e⁻
Reduction: 2 H⁺(aq) + 2 e⁻ → H₂(g)
Sn(s) undergoes oxidation so it is the reducing agent, while H⁺(aq) undergoes reduction so it is the oxidizing agent.
