Which of the following best defines a limiting reactant in a chemical reaction?

• A. The reactant that remains in excess after the reaction is complete.
• B. The product that is formed in the smallest amount during the reaction.
• C. The reactant that is completely consumed first, thus limiting the amount of product formed.
• D. The reactant present in the greatest quantity at the start of the reaction.

Answer: (C)

Verified step by step guidance

1. Understand that in a chemical reaction, reactants are substances that undergo change to form products.
2. Recognize that the limiting reactant is the one that is completely used up first during the reaction, which stops the reaction from continuing because there is no more of this reactant to react.
3. Note that the limiting reactant determines the maximum amount of product that can be formed, as the reaction cannot proceed without it.
4. Distinguish the limiting reactant from the excess reactant, which is the reactant that remains after the reaction is complete because it was not fully consumed.
5. Therefore, the best definition of the limiting reactant is: the reactant that is completely consumed first, thus limiting the amount of product formed.