The correct option is **B. Cl2**. ### Detailed Explanation: 1. **Understanding Oxidizing Agents**: - An oxidizing agent is a substance that gains electrons in a chemical reaction and, in the process, causes another substance to be oxidized. This means that the oxidizing agent itself is reduced (it undergoes a decrease in oxidation state). 2. **Analyzing the Reaction**: - The given reaction is: \[ \text{H}_2\text{O} + 2\text{Fe}^{2+} + \text{Cl}_2 \rightleftharpoons 2\text{Fe}^{3+} + 2\text{Cl}^- + \text{H}_2\text{O} \] - In this reaction, we need to identify which species is being reduced (gaining electrons) and which is being oxidized (losing electrons). 3. **Identifying Oxidation States**: - **Fe²⁺ to Fe³⁺**: The iron ion (Fe²⁺) is oxidized to Fe³⁺. This means it loses an electron: \[ \text{Fe}^{2+} \rightarrow \text{Fe}^{3+} + e^- \] - **Cl₂ to Cl⁻**: The chlorine molecule (Cl₂) is reduced to chloride ions (Cl⁻). This means it gains electrons: \[ \text{Cl}_2 + 2e^- \rightarrow 2\text{Cl}^- \] 4. **Determining the Oxidizing Agent**: - Since Cl₂ is gaining electrons and being reduced to Cl⁻, it is acting as the oxidizing agent in this reaction. It facilitates the oxidation of Fe²⁺ to Fe³⁺ by accepting electrons. ### Why the Other Options are Incorrect: - **A. Fe²⁺**: - Fe²⁺ is being oxidized to Fe³⁺, meaning it is losing electrons. Therefore, it cannot be an oxidizing agent; it is a reducing agent instead. - **C. Fe³⁺**: - Fe³⁺ is the product of the oxidation of Fe²⁺. It does not participate in the reduction process and thus cannot be an oxidizing agent. - **D. Cl⁻**: - Cl⁻ is the product of the reduction of Cl₂. Since it has already gained electrons, it cannot act as an oxidizing agent; it is a reduced form of chlorine. ### Summary of Key Points: - An oxidizing agent gains electrons and is reduced in a chemical reaction. - In the reaction provided, Cl₂ is reduced to Cl⁻, making it the oxidizing agent. - Fe²⁺ is oxidized to Fe³⁺, acting as a reducing agent. - Understanding oxidation states is crucial for identifying oxidizing and reducing agents in redox reactions. ### Revision Summary: - **Oxidizing agents gain electrons and are reduced.** - **Cl₂ is reduced to Cl⁻, making it the oxidizing agent in the reaction.** - **Fe²⁺ is oxidized to Fe³⁺, acting as a reducing agent.** - **Always check oxidation states to determine the roles of different species in redox reactions.**