Edexcel International A Level (IAL) Chemistry (YCH11) - Unit 2 - 8.6 Oxidising and reducing agents-Study Notes - New Syllabus

8.6 Oxidising Agents and Reducing Agents

In redox reactions, substances can act as oxidising agents or reducing agents depending on whether they gain or lose electrons.

Oxidising agent:

• A substance that gains electrons.
• It causes another substance to be oxidised.

Reducing agent:

• A substance that loses electrons.
• It causes another substance to be reduced.

Key Relationships

• Oxidising agent is reduced.
• Reducing agent is oxidised.

Example 1

\( \mathrm{2Na + Cl_2 \rightarrow 2NaCl} \)

• Na → \( \mathrm{Na^+ + e^-} \) (loses electrons) → reducing agent
• \( \mathrm{Cl_2 + 2e^- \rightarrow 2Cl^-} \) (gains electrons) → oxidising agent

Example 2

\( \mathrm{Mg + Cu^{2+} \rightarrow Mg^{2+} + Cu} \)

• Mg loses electrons → reducing agent
• \( \mathrm{Cu^{2+}} \) gains electrons → oxidising agent

Using Oxidation Numbers

• Oxidising agent → oxidation number decreases.
• Reducing agent → oxidation number increases.

Key Points

• Oxidising agents gain electrons.
• Reducing agents lose electrons.
• Both occur together in a redox reaction.
• Can also be identified using oxidation numbers.

Therefore, identifying oxidising and reducing agents is essential for analysing redox reactions.