In a redox reaction, the reducing agent is the substance that causes another substance to be reduced. In other words, the reducing agent is the substance that is oxidized. The oxidizing agent is the substance that causes another substance to be oxidized. In other words, the oxidizing agent is the substance that is reduced.

Common reducing agents include:

- Metals

- Non-metals

- Some organic compounds

Common oxidizing agents include:

- Halogens

- Oxygen

- Some metal ions

- Some organic compounds

In the reaction between iron metal and copper sulfate, iron metal is the reducing agent and copper sulfate is the oxidizing agent. Iron metal is oxidized to form iron(II) sulfate, and copper sulfate is reduced to form copper metal.

$$Fe_{(s)}+CuSO_{4(aq)}→FeSO_{4(aq)}+Cu_{(s)}$$