1. Bell Ringer Jan. 26 Balance the equation: Fe2O3 + Cl2  FeCl3 + O2
What is the mole ratio of:
- Fe2O3 to O2
- Cl2 to FeCl3
How many moles of chlorine are needed to produce 6 mole of Iron (III) chloride?

2. Using Mole-Mole Factors in Calculations
Calculations based on balanced equations require the use of mole to mole conversions
Equation must be balanced
Identify the known and needed substances
Make the conversion factor based on
Balanced equations are mole statements

3. Mole-Mole Factors
Determine how many moles of methanol would be produced if moles of hydrogen gas is consumed 2

4. Using Mole-Mole Factors in Calculations: Calculating Moles of a Product
Calculate the moles of CO2 formed when 4.30 moles of C3H8 reacts with O2 5 3 4
Show on the board how to calculate the 21.5 moles of oxygen, the required amount

5. Using Mole-Mole Factors in Calculations: Calculating Moles of a Product
Set up the problem using the mole-mole factor that cancels given moles and provides needed moles 5 3 4
Mole-mole factor

6. Mass Calculations for Reactions
From the balanced equation
It is also possible to start with a known mass of one substance
Then convert to moles of another substance
Start with a known amount of moles of a substance
Then convert to the sought mass of another substance

7. Mass Calculations
Convert the moles of one substance to moles of another substance
Find the mole-mole factor using the coefficients in the balanced equation
Ratios ONLY apply to moles, NOT grams
Convert grams to moles, then use mole ratio
Can also start with the mass of A and calculate the mass of B
Mole-mole
factor

8. Mass Calculations You can only relate moles of two compounds
Ratios ONLY apply to moles, NOT grams
Convert grams to moles, then use mole ratio

9. Mass Calculations For Reactions: Mass of Product from Mass of Reactant
moles C3H8
moles CO2
grams C3H8
grams CO2
MM of A
MM of B
Stoichiometry
How many moles of carbon dioxide is produced when 96.1 g of propane react with sufficient oxygen?
Plan to convert the given mass to given moles
Convert the given moles to needed moles by the use of mole-mole factor 5 3 4

10. How many moles of propane are produced when 52 g of oxygen is used?

11. Exit Ticket
Analyze the equation below, and predict how you will determine the grams of O2 from 52g of H2O? 5 3 4

12. Mass Calculations Example 1
moles C3H8
moles CO2
grams C3H8
grams CO2
MM of A
MM of B
moles A
moles B
Stoichiometry
Write the equalities
1 mol C3H8 = g C3H8
1 mol CO2 = g CO2
1 mol C3H8 = 3 mol CO2 to create mole-mole factor 5 3 4
Given: 96.1 g C3H8
Mass needed: g of CO2
Use the coefficients to write the equalities, then mole to mole factors
Equality 1 to convert moles to mass
Equality 2 to convert mass to moles
Equality 3 mole to mole ratio from the coefficients

13. Mass Calculations Example 15 3 4
X g CO2

14. Mass Calculations Example 2
What mass of carbon monoxide and what mass of hydrogen are required to form 6.0 kg of methanol by the following reaction: 2

15. Mass Calculations Example 2

16. Mass Calculations Example 2

17. Limiting Reactants
Chemical reactions with two or more reactants will continue until one of the reactants is used up
The reactant used up is called the limiting reactant (reagent)
This limits the amount of product that can be made
The reaction will stop once that reactant is gone

18. Reactions
In the lab, reactants do not always combine in exact mole ratios
Often reactions are run with more of one reactant than is needed (excess)
A reaction will continue until one of the reactants runs out
Reactant that runs out first is the Limiting Reactant
More of one reactant is an excess

19. Calculating Moles of Product from a Limiting Reactant
To determine the limiting reactant between two reactants
Balance the equation
Determine the number of moles of each reactant
Calculate the number of moles of product that each of the reactants (moles) would produce
The reactant producing the least amount of product (moles) is the limiting reactant

20. Calculating Moles of Product from a Limiting Reactant
Determine the number of moles of product that each reactant can make
The smallest number is the MAXIMUM product you can make
The reactant that gives the smallest amount of product is the limiting reactant

21. Calculating Mass of Product from a Limiting Reactant
Balance the equation
Determine the amount of product that can be made by each reactant
Compare numbers
Reagent that gives the smaller number is limiting and that is the maximum amount of product that can be made

22. Limiting Reactant Problem
Lithium nitride, an ionic compound containing Li+ and N3- ions, is prepared by the reaction of lithium metal and nitrogen gas. Calculate the mass of lithium nitride formed from 56.0 g of nitrogen gas and 56.0 g of lithium metal. 2 6

23. Limiting Reactant Problem
moles Li
moles Li3N
grams Li
Grams Li3N
MM of Li
MM of Li3N
Stoichiometry 6 3
Given: 56.0 g Li
Given: 56.0 g N2
Needed: g of Li3N
Equalities and Conversion Factors
1 mol Li = 6.941g Li
1 mol N2 = g N2
1 mol Li3N= g Li3N

24. Calculate the Limiting Reactant
8.07 mol Li
2.69 mol Li3N
Set up problem
Fewer number of moles of product with Li as reactant, so it is limiting
2.00 mol N2
4.00 mol Li3N

25. Limiting Reactant Problem
Lithium is the limiting reagent.
Calculate the number of grams of lithium nitride formed in the reaction based on the limiting reactant: 2.69 mol of lithium
93.7 g Li3N

26. Product Yield
The calculated amount of product that should be obtained is called the theoretical yield
Assumes all reactants are converted to product based on the mole-mole ratios of reactant to product
Rarely do you get the maximum amount of product
Side reactions
Loss during transfer
Accidental spills
Also impure reagents and solubility problems

27. Percent Yield Theoretical Yield The calculated amount of product
Actual Yield
The actual amount of product
Something less than the theoretical
Percent Yield
The fraction of the theoretical yield actually obtained is expressed as a percent
Theoretical based on the mole ratios

28. Percent Yield Example
In the previous limiting reactant problem, you actually produced g of Li3N. What is the percent yield of this reaction?
96.9 % yield

29. end