Define an oxidising agent as a substance that oxidises another substance and is itself reduced

🔬 Chemical Reactions – Redox

Oxidising Agent

An oxidising agent (also called an oxidiser) is a substance that takes electrons from another substance, thereby oxidising that substance. At the same time, the oxidising agent itself gains electrons and is therefore reduced.

Think of it like a superhero who steals power from a villain. The villain (the substance being oxidised) loses power (electrons), while the superhero (the oxidising agent) gains power and becomes stronger (reduced).

Key Points

• Oxidising agents are electron acceptors.
• They are always reduced in the reaction.
• Common examples: $O_2$, $KClO_3$, $HNO_3$, $Cl_2$, $Fe^{3+}$.
• In a redox equation, the oxidising agent appears on the left side of the arrow.
• Balance the equation by ensuring the same number of electrons are transferred on both sides.

Common Oxidising Agents & Their Reduction Products

Balancing a Redox Reaction (Example)

1. Write the unbalanced equation: $Fe^{3+} + e^- \rightarrow Fe^{2+}$.
2. Identify the oxidising agent: $Fe^{3+}$.
3. Balance the electrons: one electron is transferred.
4. Check that atoms and charge are balanced on both sides.

Remember: the oxidising agent always ends up with a lower oxidation state after the reaction.

Quick Quiz

Which of the following is an oxidising agent?

1. $H_2O$
2. $Na^+$
3. $Cl_2$
4. $CO_2$