Safety boundary
Use paper-token models, supplied calculations, and simulations only. No unsupervised chemical reactions are required.
Explicit chemistry instruction
A balanced equation defines the required reactant ratio. If the available amounts do not match that ratio, one reactant is consumed first and limits product formation.
The limiting reactant is identified by comparing how much product each reactant could produce, not by simply choosing the smaller mass or mole amount.
The excess reactant remains after the limiting reactant is exhausted.
Vocabulary: limiting reactant; excess reactant; stoichiometric ratio; available amount; maximum product.
Worked example
For 2A+B→C, 4 mol A requires 2 mol B. If only 1 mol B is available, B limits the reaction.
Guided question
Given 6 mol A and 2 mol B for 2A+B→C, which reactant limits?
Independent work
- Use a paper-token model for three reactant sets.
- Calculate potential product from each reactant.
- Identify limiting and excess reactants.
Misconception check
The reactant with the smaller number of moles is not automatically limiting.
Formative check
What determines the limiting reactant?
Reveal response
Which available amount produces the smaller amount of product according to stoichiometric ratios.
Mentor evidence conference
Ask Archaemenes to audit the limiting-reactant logic, conversion chain, and evidence interpretation.
Teacher guidance
Foundation: Use token and ratio tables.
Core: Solve limiting-reactant comparisons.
Extended: Analyze cases with noninteger remaining excess.