Key Concepts: Limiting Reactants

Limiting reactants are substances in a chemical reaction that determine the amount of product that can be formed.
The reactant that is completely consumed in the reaction is the limiting reactant.
Once the limiting reactant is used up, the reaction stops, no matter how much of the other reactants are left.
The amount of product formed is directly proportional to the amount of limiting reactant used. If you double the amount of the limiting reactant, you will double the amount of product.
To identify the limiting reactant in a reaction, compare the actual mole ratio of the reactants with the stoichiometric mole ratio from the balanced chemical equation.
The limiting reactant can also be determined by working out the amount of product each reactant would produce and identifying which substance would produce the least amount of product.
Understanding limiting reactants can help in predicting the theoretical yield of a chemical reaction – the maximum amount of product that could be formed from the given amounts of reactants.
This concept is important in industrial chemistry to minimize waste and maximize efficiency.
It’s crucial to remember that the excess reactant is the substance that is not entirely used up in the reaction - there will be some leftover at the end when all of the limiting reactant has been consumed.
Practical application of the concept of limiting reactants can be observed in making a sandwich. If you have 5 slices of bread and 3 slices of cheese, then the limiting reactant is the cheese, because once you’ve used each slice of cheese, you can’t make anymore sandwiches, even though you have 2 slices of bread left.