The substance oxidised is called the which agent?

• A. Oxidising agent
• B. Reducing agent
• C. Catalyst
• D. Solvent

Answer: (B)

In a redox reaction, electrons move from the species that is oxidized to the one that is reduced. The substance that loses electrons (is oxidized) is the reducing agent because it donates electrons to the other substance. So the oxidised substance is called the reducing agent.

For example, in a reaction where zinc metal goes to Zn2+ and reduces Cu2+ to copper, zinc is the reducing agent since it donates electrons and is oxidized, while Cu2+ is the oxidising agent because it gains those electrons and is reduced. The other options don’t fit: the oxidising agent is the one that gains electrons, a catalyst speeds up the reaction without being consumed, and a solvent is the medium in which the reaction occurs.