Answer:
Cl⁻ is the reducing agent.
Explanation:
The redox reaction is as follow:
MnO₂ + 4H⁺ + 2Cl⁻ → Mn²⁺ + 2H₂O + Cl₂
One should know the following terms,
Reducing agent:
An atom or element which tends to lose electron during a chemical reaction and get itself oxidized. In above reaction Cl⁻ is reducing agent as it carries a negative charge (means it has one extra electron) on the reactant side while, it has zero oxidation state on the product side. It means going from -1 to 0 the Cl lost one electron hence, it is an reducing agent according to definition.
Oxidizing Agent:
On the other hand oxidizing agent is an element or compound which tends to accepts electron(s) and get itself reduced. In above reaction Mn has an oxidation state of +4 on reactant side and after gaining electron from Cl it has changed to +2 on the product side. Hence, it has reduced but has oxidized the Cl atom so it is an oxidizing agent according to definition.
