Understanding Oxidation and Reduction

* Oxidation: Loss of electrons

* Reduction: Gain of electrons

Identifying the Oxidizing Agent

* The oxidizing agent is the species that *causes* another species to be oxidized.

* In other words, the oxidizing agent itself gets *reduced* (gains electrons).

Analyzing the Reaction

Let's break down the reaction:

* 2Br⁻ (bromide ions) → Br₂ (bromine)

* Bromide ions are oxidized because they lose electrons to form bromine.

* SO₄²⁻ (sulfate ions) → SO₂ (sulfur dioxide)

* Sulfate ions are reduced because they gain electrons to form sulfur dioxide.

Conclusion

Since the sulfate ion (SO₄²⁻) gains electrons and causes the bromide ion (Br⁻) to be oxidized, SO₄²⁻ is the oxidizing agent.