Stoichiometry involves calculating the quantitative relationships between reactants and products in a chemical reaction using a balanced chemical equation. It allows determination of mole ratios and mass relationships. Key aspects are reading the coefficients in the balanced equation in terms of moles and determining all possible mole ratios between reactants and products. The limiting reagent is the reactant that is completely used up first and thus limits the amount of product that can be formed.

1. Chapter 9- Stoichiometry:
• Stoichiometry is like
following a recipe
• Focuses on mass or
molar relationships
• Key is a balanced
equation and reading
the equation in terms
of…Coefficients
I have a yellow hat
on!
The mass relationships between reactants and products
in a chemical reaction.

2. Let’s try this:
1. Type of reaction?
2. Balanced equation
3. How is this read in terms of moles?
4. What are all the possible mole ratios?
5. “RECIPE” for moles to moles, moles to
mass, mass to moles and mass to mass
Na + Cl2

3. Let’s try this:
1. Type of reaction?
2. Balanced equation
3. How is this read in terms of moles?
4. What are all the possible mole ratios?
5. “RECIPE” for moles to moles, moles to
mass, mass to moles and mass to mass
Na + Cl2 NaCl

4. Let’s try this:
1. Type of reaction? Synthesis
2. Balanced equation
3. How is this read in terms of moles?
4. What are all the possible mole ratios?
5. “RECIPE” for moles to moles, moles to
mass, mass to moles and mass to mass
Na + Cl2 NaCl

5. Let’s try this:
1. Type of reaction? Synthesis
2. Balanced equation
3. How is this read in terms of moles?
4. What are all the possible mole ratios?
5. “RECIPE” for moles to moles, moles to
mass, mass to moles and mass to mass
2Na + Cl2 2NaCl

6. Let’s try this:
1. Type of reaction? Synthesis
2. Balanced equation
3. How is this read in terms of moles?
2 moles of Na react with 1 mole of Cl2
to produce 2 moles of NaCl
2Na + Cl2 2NaCl

7. Let’s try this:
1. What are all the possible mole ratios?
2 mol Na 2 mol Na 1 mol Cl2
1 mol Cl2 2 mol NaCl 2 mol NaCl
2 mol NaCl 2 Mol NaCl 1 mol Cl2
2 mol Na 1 mol Cl2 2 mol Na
2Na + Cl2 2NaCl

8. Let’s try this:
5. “RECIPE” for moles to moles, moles to
mass, mass to moles and mass to mass
Remember that you cannot use a mass-mass
ratio. You must convert to mol first and then
back into grams.
2Na + Cl2 2NaCl

9. Conversions of Quantities in Moles
CO2 + 2LiOH → Li2CO3 + H2O
How many moles of lithium hydroxide are
required to react with 20 moles of carbon
dioxide, the average amount exhaled by a
person each day?

10. Conversions of Quantities in Moles
CO2 + 2LiOH → Li2CO3 + H2O

11. Conversions of Quantities in Moles
CO2 + 2LiOH → Li2CO3 + H2O
2 mol LiOH
1 mol CO2

12. Conversions of Quantities in Moles
CO2 + 2LiOH → Li2CO3 + H2O
2 mol LiOH x mol LiOH
1 mol CO2 20 mol CO2
X

13. Conversions of Quantities in Moles
CO2 + 2LiOH → Li2CO3 + H2O
2 mol LiOH x mol LiOH
1 mol CO2 20 mol CO2
x 40 mol LiOH
X
=

14. More Practice
Use the following equation to determine how
many grams of aluminum must be used to
produce 5.00 grams of hydrogen gas?
2 Al(s) + 6 HCl(aq) → 2 AlCl3(aq) + 3 H2(g)

15. Do Now
In the reaction P4 + 5 O2 → 2 P2O5, how
many moles of oxygen are consumed
each time 0.500 mol of P2O5 is formed?
Answer: 1.25 mol O2

16. Limiting Reagent
Let’s pretend we have 7,000,000 hot dogs
But only 600 hot dog buns
X 1,000,000
X 100

17. Limiting Reagent
Q- How many hot dogs can you make?

18. Limiting Reagent
Q- How many hot dogs can you make?
A – Only 600

19. Limiting Reagent
Once a reactant is used up, there can
be no more products produced
(The substance that is used up first is called the)
limiting reagent =
the reactant that limits the amount of the other
reactant that can be combined and thus the
product that is produced
Excess reagent =
the substance not used up completely

20. Let’s try a problem:
HCl + NaOH NaCl + H2O
2 mol 2.5 mol
Determine the limiting reagent for this reaction.
(This is done by comparing the 2 given value in
a ratio.)

21. Let’s try a problem:
HCl + NaOH NaCl + H2O
2 mol 2.5 mol
Pick one of the givens and solve:
1 mol HCl x mol HCl
1 mol NaOH 2.5 mol NaOH
x 2.5 mol HCl
=
=

22. Let’s try a problem:
HCl + NaOH NaCl + H2O
2 mol 2.5 mol
2.5 mol HCl: But what does this mean?
This means that in order to react ALL
2.5 mol NaOH, you would need AT LEAST
2.5 mol HCL.
But you only have 2 mol HCl, so it LIMITS
the reaction. Hence: limiting reagent.

23. Percentage Yield
• Theoretical yield = what you calculate or
expect under perfect conditions
• Actual Yield = what you get in the lab
• Percentage Yield = x 100%
Actual Yield
Theoretical Yield