Which of the following best describes the role of a reducing agent in a chemical reaction?

• A. It donates electrons to another substance and is itself oxidized.
• B. It accepts electrons from another substance and is itself reduced.
• C. It increases the oxidation state of another substance by removing electrons.
• D. It acts as a catalyst without undergoing any change in oxidation state.

Answer: (A)

Verified step by step guidance

1. Understand the definition of a reducing agent in redox (reduction-oxidation) reactions: a reducing agent is a substance that causes another substance to be reduced by donating electrons to it.
2. Recall that when a substance donates electrons, it loses electrons and therefore undergoes oxidation itself. This means the reducing agent is oxidized during the reaction.
3. Contrast this with an oxidizing agent, which accepts electrons and is itself reduced.
4. Recognize that increasing the oxidation state of another substance involves removing electrons from it, which is the role of a reducing agent, but the key point is that the reducing agent donates electrons and is oxidized.
5. Note that a catalyst facilitates a reaction without changing its own oxidation state, so it does not fit the role of a reducing agent.