Which of the following statements about a limiting reagent is correct?

• A. It is the reactant present in the greatest amount.
• B. It is the reactant that is completely consumed first in a chemical reaction.
• C. It determines the excess amount of product formed.
• D. It is always the reactant with the lowest molar mass.

Answer: (B)

Verified step by step guidance

1. Understand the concept of a limiting reagent: In a chemical reaction, the limiting reagent is the reactant that is completely consumed first, thus limiting the amount of product that can be formed.
2. Recognize that the limiting reagent is not necessarily the reactant present in the greatest amount; it depends on the stoichiometric ratios of the reactants, not just their quantities.
3. Note that the limiting reagent determines the maximum amount of product formed, not the excess amount; the excess reagent is the one left over after the reaction is complete.
4. Understand that the limiting reagent is not related to the molar mass of the reactants; it depends on the mole ratio and amounts used in the reaction.
5. Therefore, the correct statement is: 'It is the reactant that is completely consumed first in a chemical reaction.'