Limiting reactants (RAM 1 d.p.)
I can identify a reactant as an excess or limiting reactant and use that information to calculate a theoretical yield.
Limiting reactants (RAM 1 d.p.)
I can identify a reactant as an excess or 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 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 is 6.02 × 10²³ particles of it. The mass of a 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.
To help you plan your year 10 chemistry lesson on: Limiting reactants (RAM 1 d.p.), download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 10 chemistry lesson on: Limiting reactants (RAM 1 d.p.), download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 chemistry lessons from the Calculations involving masses unit, dive into the full secondary chemistry curriculum, or learn more about lesson planning.
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
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