1. Stoichiometry: Limiting Reactant
Ms. Samayoa
Birmingham Community Charter High School
Chemistry

2. Learning Objective: Students will be able to identify a limiting reactant and excess reactants from a set of reactants.
Academic Vocabulary: limiting reactant and excess reactant

3. Limiting Reactants Analogy
To understand limiting reactants, let’s first observe the parts of a burger

4. Limiting Reactants Analogy
To make a burger you need:
1 bun
1 slice of cheese
1 patty
1 lettuce leaf
Write the “recipe” for a burger in chemical equation form and identiffy the reactants and the products

5. Recipe into Chemical Equation
1 bun + 1 slice of cheese + 1 lettuce leaf + 1 patty  1 burger

6. Limiting Reactants Analogy
Discuss with a partner what is the greatest number of burgers that can be made with the following number of ingredients

7. Limiting Reactant Analogy
Despite there being 4 buns, 6 slices of cheese, and 5 patties, we can only make 3 burgers because there are only 3 lettuce leafs
The lettuce leaf is known as the limiting reactant

8. Limiting Reactant
The limiting reactant is the first reactant that is used up in a reaction
When the limiting reactant is all used up, no more product can form, and the reaction stops

9. Limiting Reactant Analogy
After making the burgers, the ingredients left over are buns, slices of cheese, and patties
Because they are left over, they are known as excess reactants

10. Excess Reactants
Excess reactant is what is left over after the reaction stops because the limiting reactant got all used up

11. Check for Understanding
Below is the recipe to make a ham and cheese sandwich: 1 slice of ham + 1 slice of cheese + 2 slices of bread  1 ham&cheese sandwich If I had 3 slices of ham, 4 slices of cheese, and 4 slices of bread, which ingredient will be my limiting reactant and which ingredient will be my excess reactant?

12. S’mores Lab

13. Example Problem
2H2 + O2  2H2O
If you start with 10 g of H2 and 5 g of O2, determine the limiting reagent.

14. Check for Understanding
4Fe + 3O2  2Fe2O3
If you start with 10 g of Fe and 5 g of O2, determine the limiting reagent.