Question 18

The term for the reactant that is entirely consumed in a reaction is the limiting reactant.

In a chemical reaction, the limiting reactant is the substance that is completely used up when the reaction goes to completion, thereby determining the maximum amount of product that can be formed.

A) limiting reactant

This option is correct because the limiting reactant is specifically defined as the reactant that is entirely consumed in the course of the reaction. Once this reactant is depleted, the reaction cannot proceed further, regardless of the amounts of other reactants present.

B) reducing agent

The reducing agent is incorrect in this context as it refers to a substance that donates electrons in a chemical reaction, leading to the reduction of another substance. While it may be consumed during a reaction, it does not specifically denote the reactant that is entirely consumed overall.

C) reaction intermediate

This option is also incorrect because a reaction intermediate is a transient species formed during the reaction process that is not present in the final products. It is not a reactant that is consumed entirely but rather a temporary state that exists between reactants and products.

D) reagent

While the term reagent can refer to any substance used in a chemical reaction, it does not specifically indicate that the substance is entirely consumed. Reagents can be present in excess and may not limit the reaction, making this choice incorrect for the definition sought in the question.

Conclusion

The limiting reactant is the essential term for identifying the reactant that is consumed completely in a reaction, as it determines the yield of products. All other options describe different aspects of chemical reactions but do not fit the specific definition required by the question, making them incorrect.