In a chemical reaction, the substance that causes oxidation by removing electrons from another substance is called the

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

Answer: (C)

In redox reactions, one substance is oxidized (loses electrons) and another is reduced (gains electrons). The substance that causes the oxidation by accepting electrons from the other is the oxidizing agent. It pulls electrons away from the other compound, which makes the other substance oxidized, and in the process the oxidizing agent itself is reduced. So the oxidizing agent is the acceptor of electrons, the one that drives the oxidation of the partner.

For contrast, a reducing agent donates electrons to another substance, causing that substance to be reduced, and the reducing agent itself becomes oxidized. Catalysts speed up reactions without being consumed, and solvents simply provide the medium for the reaction. A common example is chlorine gas acting as the oxidizing agent when it takes electrons from iodide, oxidizing iodide to iodine while chlorine is reduced to chloride.