What does the term 'excess reactants' imply about the reaction mixture?

• A. The excess reactants mean that some of the reactant remains after the reaction
• B. All reactants are consumed completely
• C. The reaction does not proceed
• D. The product yield is zero

Answer: (A)

Excess reactants means there is more of one reactant than is needed to react with the others. In a reaction, the amount of product formed is limited by the reactant that runs out first (the limiting reactant). Once that limiting reactant is used up, any remaining excess reactant cannot all react because there’s not enough of the other reactants to combine with it, so some of the excess stays in the mixture after the reaction is finished. That’s why the correct statement is that some of the reactant remains after the reaction.

The other ideas would only be true in different situations: if all reactants were consumed completely, there wouldn’t be excess; the reaction can still proceed even with excess until the limiting reactant is used up; and the product yield isn’t necessarily zero just because there’s excess—there can still be product formed up to the amount dictated by the limiting reactant.