1. Stoichiometry
The calculation of quantities in chemical equations.
Interpreting balanced chemical equations

2. The large whole numbers out in front
Coefficients
What are they?
What do they represent?
Write a sentence describing this equation.
N2 + 3H2  2NH3
The large whole numbers out in front
The # of particles (atoms, molecules)
The # of moles of each substance
1 mole of Nitrogen gas reacts with 3 moles of Hydrogen gas to produce 2 mole of ammonia

3. Why we do this
Translate a chemical equation to units that can be used in the lab. (mass = grams)
3 Step Process
Mass of Given to Moles of Given
Moles of Given to Moles of Unknown.
Moles of Unknown to Mass of Unknown

4. Mole  Mole
Calculations
Converting from moles of one substance to moles of another, using a balanced chemical equation.

5. Relationship between the coefficients in a balanced chemical equation.
Molar Ratios
Example
Relationship between the coefficients in a balanced chemical equation.
Used to determine the relative amount of each substance needed.
N2 + 3H2  2NH3
Molar Ratio of N2 to H2 =
Molar Ratio of N2 to NH3 =
Molar Ratio of H2 to NH3 =

6. Mole  Mole
Calculations
N2 + 3H2  2NH3
How many moles of ammonia (NH3) are produced when 0.60 moles of nitrogen react with hydrogen?
Calculate the number of moles of nitrogen required to make 7.24 moles of ammonia?

7. Mass-Mass
W.S. Mass-Mass/ Volume-Volume

8. Model 3: The Balanced Chemical Equation

9. Brain Teaser Be + 2 HCl  BeCl2 + H2
Given 1.20g of Be, how many grams of Beryllium Chloride was produced? If my actual yield was 4.5 grams, what was my percent yield?

10. Limiting Reactants Limiting reactant
Reactant that is completely used up in a chemical reaction
Determines the maximum amount of product that can be formed.

11. Limiting Reactants Why is this important?
The quantities of products formed in a reaction are always determined by the quantity of the limiting reactant.

12. Limiting Reactants
Analogy: making cheese sandwiches

13. Limiting Reactants

14. Limiting Reactants

15. What is the limiting reactant?
Limiting Reactants
2H2 + O2  2H2O
What is the limiting reactant?

16. What is the limiting reactant?
Limiting Reactants
2H2 + O2  2H2O
What is the limiting reactant?

17. What is the limiting reactant?
Limiting Reactants
2H2 + O2  2H2O
What is the limiting reactant?

18. Limiting Reactants Zn + HCl  Demo Write a balanced chemical equation.
What is the limiting reactant?
How do you know?
Zn HCl 

19. Determining the Limiting Reactant
* The limiting reagent may not be obvious!!

20. Example
If 3.5 grams of copper are added to a solution containing 6.0 grams of silver nitrate. What is the limiting reagent and how much silver can be produced?
Cu + 2AgNO3  Cu(NO3)2 + 2Ag

21. Example
Identify the limiting reactant when 1.7 g of sodium reacts with 2.6 L of chlorine gas at STP to produce sodium chloride.

22. Quiz 1) CaCl2 + Na2CO3  CaCO3 + 2NaCl
5.45 g g ? ? 111 g/mol g/mol g/mol g/mol How much CaCO3 (in g) is formed?
2) CaCl Na2CO3  CaCO NaCl mol mol ? ? How many moles of each product could be produced?

23. Can you really get out everything that goes in?
% yield = experimental yield x 100
theoretical yield
Experimental or actual yield determined in the lab
Theoretical or expected yield determined by stoichiometry

24. Group Quiz
CaCl Na2CO3  CaCO NaCl mol L at STP ? ? How many moles of each product could be produced?
2) CaCl Na2CO3  CaCO NaCl
5.45 g g ? How much CaCO3 (in g) is formed? What is the percent yield for this reaction if 3.96 g of calcium carbonate was isolated from the reaction?

25. How efficient are you in the lab?
Work as a team
Each group member must perform one of the reactions.
Calculate each individuals efficiency as well as your group average.
Each group member is responsible for their own lab report

26. How efficient are you in the lab?
To turn in
Each group member is responsible for showing the work for their own experiment. Calculation of theoretical yield, measured experimental yield and percent yield calculation.
Where did the errors occur? What would you do differently if hired by the company?
If you owned the company would you hire us? Why or why not. Explain with data to support your answer.
What would you observe if the solution were not in excess? What would be different?