1. Using Stoichiometry
Chemists use stoichiometry to predict amounts of reactants used and products formed in specific reactions

2. Always start with a balanced equation
This tells you the correct amount of moles for each substance
N₂ + 3H₂ → 2NH₃
Like a recipe

3. Peanut Butter Cookies 1 cup butter 1 tsp
Peanut Butter Cookies 1 cup butter 1 tsp. vanilla 1 cup sugar 3 cups flour 1 cup brown sugar 2 tsp. baking soda 2 eggs ¼ tsp. salt 1 cup peanut butter makes 24 cookies
What if I need 48 cookies?
What if I want only 12 cookies?
What if I need 5 dozen?
If 3 cups of peanut butter are used, how many cookies will I get?

4. 2K + 2H₂O → 2KOH + H₂
Potassium reacts with water to produce potassium hydroxide and hydrogen
2 mol potassium makes
1 mol hydrogen
How much hydrogen is produced
if only mol of potassium is
used?

5. Review mole ratios 2K + 2H₂O → 2KOH + H₂
Which two ratios deal with potassium
and hydrogen?

6. Mole to Mole Conversion
1. balance equation 2. Use correct mole ratio
Moles of known x Moles of unknown = Moles of
Moles of known unknown

7. Moles of known x Moles of unknown = Moles of
2K + 2H₂O → 2KOH + H₂
Moles of known x Moles of unknown = Moles of
Moles of known unknown
mol K x 1 mol H₂ = mol H₂ 2 mol K

8. Try it!
One disadvantage of burning propane (C₃H₈) is that carbon dioxide (CO₂) is one of the products. How many moles of CO₂ is produced when 10.0 mol of C₃H₈ is burned in excess oxygen in a gas grill?
What is first step?

9. Moles of known x Moles of unknown = Moles of
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
Use correct mole ratio
Moles of known x Moles of unknown = Moles of
Moles of known unknown

10. Mole to Mass Conversion
If you know the moles of a reactant and you want to know the mass of a product
Mole to Mass Conversion

11. Mole to Mass Conversion
Balance equation
Use correct mole ratio
Multiply by molar mass

12. What is the mass of NaCl when Na reacts with 1.25 mol Cl gas?
1. Balance the equation

13. 2Na + Cl₂ = 2NaCl 2. Use correct mole ratio
1.25 mol Cl₂ x 2 mol NaCl = mol NaCl
1 mol Cl₂

14. 2.50 mol NaCl 3. Multiply by molar mass
2Na + Cl₂ = 2NaCl
2.50 mol NaCl 3. Multiply by molar mass

15. Mass to Mass Conversions
When working in a lab, you will be working with grams to measure out substances…
Mass to Mass Conversions

16. Mass to Mass Conversions
Balance equation
Convert grams to moles of known substance
Use correct mole ratio
Multiply by molar mass

17. MacGyver saves the day again!
MacGyver offers to help some criminals break into an armored vehicle in order to save a life
Chemistry in Action!!!

19. Mass to Mass Conversion
3Mg + Fe₂O₃ → 3MgO + 2Fe + lots of heat
How many grams of Mg does MacGyver need to make 5.0 g of Fe?

20. 3Mg + Fe₂O₃ → 3MgO + 2Fe + heat
Balance equation
Convert grams to moles of known substance
5.0 g Fe = ? Mol / molar mass Fe

21. Moles of known x Moles of unknown = Moles of
5.0 g Fe = mol Fe
3. Use correct mole ratio
3Mg + Fe₂O₃ → 3MgO + 2Fe + heat
Moles of known x Moles of unknown = Moles of
Moles of known unknown

22. 0.134 mol Mg
4. Multiply by molar mass x = 3.26 g Mg

23. Review

24. Worksheet!