Which statement best defines a reducing agent?

• A. The species that gets oxidized acts as reducing agent
• B. The species that gets reduced acts as reducing agent
• C. A substance that decreases the hydrogen ion concentration
• D. A substance that does not participate in redox reactions

Answer: (A)

A reducing agent is the substance that donates electrons to another species during a redox reaction, and in doing so it itself becomes oxidized. That means the species that loses electrons is the one acting as the reducing agent. The entity that gains electrons is the oxidizing agent, not the reducing agent. Statements about lowering hydrogen ion concentration describe basicity, not redox behavior, and something that doesn’t participate in redox reactions cannot be a reducing agent. So the description that the species that gets oxidized acts as the reducing agent correctly captures the defining role.