Learning focus
Explain chemical changes using particles, collisions, equilibrium and electron transfer; interpret graphs and industrial conditions; and apply the ideas to unfamiliar reactions.
Oxidising agent
An oxidising agent oxidises another substance and is itself reduced. It accepts electrons or supplies oxygen. In Zn + Cu2+ -> Zn2+ + Cu, Cu2+ is the oxidising agent because it accepts electrons and is reduced.
Reducing agent
A reducing agent reduces another substance and is itself oxidised. It donates electrons or removes oxygen. Zinc is the reducing agent in the same reaction because it loses electrons.
Avoiding name confusion
The agent is named for the change it causes, not the change it undergoes. Therefore the oxidising agent undergoes reduction, and the reducing agent undergoes oxidation.
Using half-equations
A species on the electron-reactant side of a reduction half-equation is accepting electrons and may act as an oxidising agent. A species producing electrons in an oxidation half-equation may act as a reducing agent.
Practical or data skill
For each redox equation, identify the oxidised species, reduced species, oxidising agent and reducing agent in a four-column table.
Examination tip
Check your answer by stating the change undergone by the proposed agent.
Review questions and suggested answers
Question 1
What happens to an oxidising agent?
Suggested answer
It is reduced.
Question 2
What happens to a reducing agent?
Suggested answer
It is oxidised.
Question 3
Which agent accepts electrons?
Suggested answer
The oxidising agent.
