1. Limiting Reactants
Chemistry
Unit 4.5, Day 3

2. M&M Opening Element Do NOT eat any M&M’s yet
Make as many of the following groups:
1 Red
2 Blue
3 Green
2 Yellow
How many groups did you make?
Which of the above colors did you run out of first?
Which colors do you have left over?
How does this relate to Chemistry?

3. Relating M&M’s to Chemistry
Think of each color M&M as a reactant
Think of the final group as the product
Why did you stop making “products”
In other words, why did you stop making new groups?

4. Why Do Reactions Stop? Limiting Reactants: Excess Reactants:
The reactant which limits the extent of the reaction, and therefore determines the amount of product produced
Excess Reactants:
The left-over reactants

5. Illustrating the Chemical Concept
3N2 + 3H2  2NH3 + 2N2
Interested in finding the amount of NH3
Break down each compound into atoms
6N + 6H  2N + 6H
Which element has atoms left over?
Excess Reactant
Which element was completely used up?
Limiting Reactant

6. Determining the Limiting Reactant
S8 + 4Cl2  4S2Cl2
Rxn: 200g Sulfur reacts with 100g Chlorine NOTE: Mass of S8 = 256g/mol; Mass of Cl2 = 70g/mol
Determine the number of moles of each reactant

7. Determining the Limiting Reactant
Determine if the reactants are in the correct mole ratio as given by the balanced equation
Equation’s Mole Ratio:
Actual Mole Ratio:
4 mol Cl2
1 mol S8

8. Determining the Limiting Reactant
Identify the reactant which does not match it’s required amount
Limiting Reactant: ____
Excess Reactant: ____

9. Determining Amount of Product
Even though you are given both amounts of reactants, you can ONLY use the Limiting Reactant’s amount to calculate the product’s mass:

10. Determining Amount of Product
Helpful Information:
Mass of Cl2 = 70g/mol
Mass of S2Cl2 = 135g/mol

11. Checks for Understanding
P4 + 5O2  P4O10
Which is the Limiting Reactant?
Which is the Excess Reactant?
Determine the amount of P4O10 produced when 25g of P4 reacts with 50g of O2.
Helpful Information:
P4 Molar Mass = 124 g/mol
O2 Molar Mass = 32 g/mol
P4O10 Molar Mass = 284 g/mol

12. Guided Practice: Think-Pair-Share
For each of the following reactions:
Determine the Limiting Reactant
Determine the Excess Reactant
Determine the amount of Product
6Na + Fe2O3  3Na2O + 2Fe
100g Na reacts with 100g Fe2O3, determine the amount of Fe produced
Na Molar Mass = 23g/mol
Fe2O3 Molar Mass = 160g/mol
Fe Molar Mass = 56g/mol

13. Guided Practice: Think-Pair-Share
For each of the following reactions:
Determine the Limiting Reactant
Determine the Excess Reactant
Determine the amount of Product
2. 6CO2 + 6H2O  C6H12O6 + 6O2
88g CO2 reacts with 64g H2O,
determine the amount of C6H12O6 produced
CO2 Molar Mass = 44g/mol
H2O Molar Mass = 18g/mol
C6H12O6 Molar Mass = 180g/mol

14. Guided Practice: Think-Pair-Share
For each of the following reactions:
Determine the Limiting Reactant
Determine the Excess Reactant
Determine the amount of Product
3. 8P4 + 3S8  8P4S3
100g P4 reacts with 100g S8,
determine the amount of P4S3 produced
P4 Molar Mass = 124g/mol
S8 Molar Mass = 256g/mol
P4S3 Molar Mass = 220g/mol

15. Guided Practice: Think-Pair-Share
For each of the following reactions:
Determine the Limiting Reactant
Determine the Excess Reactant
Determine the amount of Product
4. Cl2 + C6H6  C6H5Cl + HCl
45g Cl2 reacts with 45g C6H6,
determine the amount of C6H5Cl produced
Cl2 Molar Mass = 70g/mol
C6H6 Molar Mass = 78g/mol
C6H5Cl Molar Mass = 112g/mol

16. Guided Practice: Think-Pair-Share
For each of the following reactions:
Determine the Limiting Reactant
Determine the Excess Reactant
Determine the amount of Product
5. Ni + 2HCl  NiCl2 + H2
5g Ni reacts with 25g HCl,
determine the amount of NiCl2 produced
Ni Molar Mass = 59g/mol
HCl Molar Mass = 35g/mol
NiCl2 Molar Mass = 129g/mol

17. Independent Practice:
Complete the following questions
Work quietly with your partner
This worksheet is due NEXT class
Raise your hand if you have questions!