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: \$O2\$, \$KClO3\$, \$HNO3\$, \$Cl2\$, \$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\$

Answer: \$Cl_2\$ (it accepts electrons and is reduced to \$Cl^-\$).