Lesson Plan: C1.5.07

Hamble Lesson Observation Plan
Learning About
What is a limiting factor?
Keywords:
  • Excess: more chemical than required for the reaction to go to completion. (1)
  • The limiting reagent (or limiting reactant, LR) in a chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by this reagent, since the reaction cannot continue without it (1)
  • Limiting factor: Search Results (1)
Memory Anchor:
Method Precise Learning Objective Linked Question / Activity
(Designed for maximum working out)		 Stepping Stones Pitstop Check
(Thinking Map)
In a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactant is used. (HT only)What is meant when a reactant is said to be in excess?

Define the term limiting reactant. Link the limiting reactant to the number of moles. Link the limiting reactant to the masses in grams. Use a small strip of magnesium ribbon in 20 ml HCl acid. Identify which reactant is the limiting reactant and state the reason for this choice.
The reactant that is completely used up is called the limiting reactant because it limits the amount of products. What is meant when a reactant is described as a limiting reactant?
Students should be able to explain the effect of a limiting quantity of a reactant on the amount of products it is possible to obtain in terms of amounts in moles or masses in grams. (HT only) 2H2 O2 --> 2H2O You react 10g of oxygen with 10g of hydrogen. Only 11.25g of product is made the rest of the reactants remain unused. Suggest why the full mass of reactants did not react. What is the leftover unreacted substance?
Links To the Big Ideas
ForcesParticlesEnergyCells