The limiting reactant in a chemical reaction is the one that
- A. is present in the largest amount by mass
- B. is completely used up first and so determines the amount of product formed
- C. has the highest molar mass
- D. remains unreacted at the end
Explanation
The reaction stops when one reactant runs out, so that reactant fixes the maximum yield no matter how much of the others is present. It must be identified by comparing moles against the balanced equation, not by comparing masses, because a small mass of a light reactant can be many moles. The reactant left over at the end is the excess reactant.