Limiting reactants
I can identify a reactant as being in excess or the limiting reactant and use that information to calculate a theoretical yield.
Limiting reactants
I can identify a reactant as being in excess or the limiting reactant and use that information to calculate a theoretical yield.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- In a chemical reaction, the atoms in reactants are rearranged and are the same atoms that are in the products.
- A theoretical yield is calculated using the stoichiometry of a balanced equation & relevant mathematical relationships.
- The number of moles of limiting reactant available is used to calculate the theoretical yield of a reaction.
- If a reactant is added in excess, not all of it will react and some will be found in the final product mixture.
- A limiting reactant is one that restricts the amount of product that can form from the available particles.
Keywords
Limiting reactant - The reactant that completely reacts, thereby determining the maximum amount of product that can be formed in a chemical reaction. All other reactants will be present in excess.
Excess reactant - Any reactant present in a greater amount than is necessary to completely react with the limiting reactant.
Theoretical yield - The maximum calculated mass of product expected to form from a given amount of reactants.
Mole - A mole of a substance contains 6.02 × 10²³ particles of it. The mass of one mole of a substance is its relative mass in grams.
Stoichiometry - The molar ratio of the reactants to the products in a chemical reaction.
Common misconception
Pupils sometimes fail to understand that excess reactant particles remain in the reaction mixture after the reaction.
Provide a balanced equation and challenge pupils to draw diagrams of a final mixture, stressing that excess particles would also be present. Challenge pupils to consider how the product could be extracted from the excess particles.
Equipment
2 cm strip of Mg crucible + lid balance tongs heatproof mat, Bunsen burner, tripod clay triangle
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Starter quiz
6 Questions
the average mass of the atoms of an element compared to carbon-12
the sum of the relative atomic masses of all the atoms in a formula
the number of particles in one mole of a substance
Exit quiz
6 Questions
the reactant that completely reacts during a reaction
a reactant that is left over at the end of the reaction
the maximum calculated mass of product expected from a reaction
the unit for amount of substance