Limiting Reagent Calculator

Limiting Reagent Calculator

Reactants

Products

What is a Limiting Reagent?

In a chemical reaction, the limiting reagent (or limiting reactant) is the substance that is completely consumed first, causing the reaction to stop. It dictates the maximum amount of product that can be formed.

Think of it like baking a cake. If a recipe calls for 2 cups of flour and 1 cup of sugar, but you only have 1 cup of flour and 10 cups of sugar, the flour is your limiting reagent. You can only make half a cake, regardless of how much extra sugar (the excess reagent) you have.

Key Concepts

  • Theoretical Yield: This is the maximum amount of product that can be created from the given amounts of reactants, assuming the reaction is 100% efficient. It is calculated based on the limiting reagent.
  • Excess Reagent: This is any reactant that is left over after the limiting reagent has been completely used up.

Frequently Asked Questions

Why do I need a balanced equation?

The balanced chemical equation provides the mole ratio (the stoichiometric coefficients) between reactants and products. Without this ratio, it's impossible to know how much product can be made from a certain amount of reactant. It's the "recipe" for the reaction.

What's the difference between theoretical yield and actual yield?

Theoretical yield is what this calculator finds—the maximum possible amount of product in a perfect world. Actual yield is the amount you *actually* get when you perform the experiment in a lab. The actual yield is almost always lower than the theoretical yield due to side reactions, incomplete reactions, or loss of product during collection.

What is percent yield?

Percent yield is a measure of a reaction's efficiency. It is calculated by dividing the actual yield (from your experiment) by the theoretical yield (from this calculator) and multiplying by 100.
% Yield = (Actual Yield / Theoretical Yield) * 100

Do all reactants have to be in grams?

Yes, for this calculator, all initial amounts must be in grams. The calculation converts these masses to moles, which is the universal unit for stoichiometric calculations, before determining the limiting reagent.