1. Stoichiometry

2. Inquiry Activity
Using 20 white balls (H), make 10 diatomic molecules. Make diatomic molecules using the yellow balls as well.
Without looking, have someone choose 10 molecules at random.
Out of the chosen molecules, pair up the reactants using the following chemical equation: Y W2  2YW3
Pair up reactants until you run out of one of the reactants. This is your limiting reagent.
Repeat the activity and see if you get the same results

3. Review – Balance these equations
N2 + H2  NH3
H2S O2  SO H2O
H I2  HI

4. Stoichiometry
Study of the amount of substances consumed or produced in a chemical reaction
– Requires Balanced Equations!
Reactants  Products

5. Reactants and Products Reactants and Products SOMETIMES the same
Stoichiometry
Reactants and Products
ALWAYS the same
Reactants and Products SOMETIMES the same
Number of Atoms
Mass
Number of molecules
Moles
Volume
N H2  NH3
Atoms N H = N H
Mass 28g g = g
Number of
molecules 1 molecule molecules molecules
Moles 1mole moles moles
Volume L L L

6. What is conserved in each reaction. Atoms. Mass. Number of Molecules
What is conserved in each reaction? Atoms? Mass? Number of Molecules? Moles?
H O2  H2O
H I2  2HI
C2H2 + O2  CO2 + H2O

7. Calculations
Mole ratio: Conversion factor using the coefficients of balanced chemical equations
Used to convert between moles of reactant and moles of product
N H2  2NH3
1 mol 3 mol 2mol
So…..
1 mol N2 2 mol NH3 3mol H2
3 mol H2 1 mol N2 2 mol NH3

8. How many moles of ammonia (NH3) are produced when 0
How many moles of ammonia (NH3) are produced when 0.6mol nitrogen (N2) reacts with hydrogen (H2)?
Write the chemical reaction:
What conversion do you use to get from N2 to NH3?
Solve

9. Al O2  Al2O3
How many moles of aluminum are needed to form 3.7mol of aluminum oxide?
How many moles of oxygen are required to react completely with 14.8mol Al?
How many moles of Al2O3 are formed when 0.78 mol O2 reacts with aluminum?

10. Mole – Mass Calculations
Calculate the number of grams of NH3 produced by the reaction of 5.40g hydrogen with an excess of nitrogen.
What is the chemical reaction?
Conversion
gram hydrogen  mol hydrogen  mol NH3  gram NH3

11. CaC H2O  C2H Ca(OH)2
How many grams of acetylene gas (C2H2) are produced by adding water to 5.00g CaC2?
How many moles of CaC2 are needed to react completely with 49.0g H2O?

12. ALYWAYS CONVERT THROUGH USING MOLES!!!
Other conversions…
Number of particles mol
6.02x1023 particles
Volume of gas at STP mol
22.4L
So you should be able to convert:
mass-mass mol-mol
mass-mol mol-number of particles
mol-volume of gas at STP
ALYWAYS CONVERT THROUGH USING MOLES!!!

13. How many molecules of oxygen are produced when 29
How many molecules of oxygen are produced when 29.2g of water is decomposed? H2O  H O2
How many grams of nitrogen dioxide must react with water to produce 5.0x1022 molecules of nitrogen monoxide?
NO H2O  HNO NO

14. How many liters of nitrogen dioxide are produced when 34L of oxygen reacts with excess nitrogen monoxide?
NO O2  NO2

15. How much do you actually get?
In any reaction, the amount of product formed is limited by the amount of reagents….
Limiting Reagent: -determines the amount of product that can be formed
-is completely used up in the reaction
Excess Reagent: reactant is not completely used up

16. What is the limiting reagent when 80g of Cu reacts with 25g of S in the following reaction?
Cu S  Cu2S
Balance the equation
Convert grams to moles
What is the mole ratio between Cu and S?
Take the given mole quantity for one reagent (#2), multiply it by the mole ratio (#3) to find how many moles of the other reagent are needed
Compare moles needed to moles you have to find which one is limiting

17. What is the limiting reagent if 6.0g HCl reacts with 5.0g Mg?
If 2.70mol of C2H4 is reacted with 6.30mol O2, what is the limiting reagent?
C2H O2  CO H2O
What is the limiting reagent if 6.0g HCl reacts with 5.0g Mg?
Mg + HCl  MgCl H2

18. Limiting reagents can be used to find out how much product is actually made.
What is the maximum number of grams of Cu2S that can be formed when 80.0 g Cu reacts with 25.0g S?
Cu S  Cu2S
What is the limiting reagent?
Use the limiting reagent to calculate the amount of product

19. How many grams of water can be produced by the reaction of 2
How many grams of water can be produced by the reaction of 2.40mol C2H2 with 7.4mol O2?
C2H2 + O2  CO H2O
If 2.7mol C2H4 is reacted with 6.3mol O2, how many moles of water are produced?
C2H O2  CO H2O

20. Things happen in lab…
Theoretical yield: the maximum amount of product that could be formed
Actual yield: the amount of product that is actually formed in lab
Percent Yield = Actual yield x 100%
Theoretical yield

21. What is the percent yield if 13. 1g CaO is actually produced when 24
What is the percent yield if 13.1g CaO is actually produced when 24.8g CaCO3 is heated?
CaCO3  CaO + CO2