Which best describes the oxidizing agent in this reaction?
[tex]\[ Cl_2(aq) + 2 Br^{-}(aq) \longrightarrow 2 Cl^{-}(aq) + Br_2(aq) \][/tex]

A. Bromine \((Br)\) is the oxidizing agent because it gains an electron.
B. Bromine \((Br)\) is the oxidizing agent because it loses an electron.
C. Chlorine \((Cl)\) is the oxidizing agent because it gains an electron.
D. Chlorine [tex]\((Cl)\)[/tex] is the oxidizing agent because it loses an electron.



Answer :

To determine which species is the oxidizing agent in the given reaction, we need to understand the concepts of oxidation and reduction:

[tex]\[ Cl_2(aq) + 2Br^-(aq) \rightarrow 2Cl^-(aq) + Br_2(aq) \][/tex]

Oxidation is the process of losing electrons.
Reduction is the process of gaining electrons.
* The oxidizing agent is the substance that gets reduced (i.e., it gains electrons).

Let's analyze the reaction step by step:

1. Identify the oxidation states of the elements in the reaction:
- \( Cl_2 \): Each chlorine atom is in the 0 oxidation state in \( Cl_2 \) because it is in its elemental form.
- \( Br^- \): Each bromine ion is in the -1 oxidation state.
- \( Cl^- \): Each chloride ion is in the -1 oxidation state.
- \( Br_2 \): Each bromine atom in \( Br_2 \) is in the 0 oxidation state.

2. Determine the change in oxidation states:
- Chlorine (\( Cl_2 \)) changes from 0 to -1 by gaining electrons. This is a reduction process.
- Bromide ions (\( Br^- \)) change from -1 to 0 by losing electrons. This is an oxidation process.

3. Identify the species involved in the redox processes:
- Chlorine (\( Cl_2 \)) is reduced since its oxidation state decreases from 0 to -1.
- Bromide (\( Br^- \)) is oxidized since its oxidation state increases from -1 to 0.

4. Determine the oxidizing agent:
- The oxidizing agent is the substance that gets reduced, which means it gains electrons.

In this reaction:
- Chlorine (\( Cl_2 \)) gets reduced to chloride ions (\( Cl^- \)) by gaining electrons.

Therefore, the correct description of the oxidizing agent is:
- Chlorine (\( Cl \)) is the oxidizing agent because it gains an electron.

Thus, from the options provided, the correct choice is:
- Chlorine (\( Cl \)) is the oxidizing agent because it gains an electron.

Given the initial analysis and understanding of the redox process, we can conclude that the answer is:

[tex]\[ \boxed{3} \][/tex]