1. Stoichiometry
Unit 6
Nov. 26th - Dec. 14th

2. Mole Island Map Mole Island Mainland Mass Particle Paradise
PT Parkway
Mole Island
Particle Paradise
Volcano o’ Volume

3. Converting Mass to Mole
Multiply mass by molar mass conversion
Divide by molar mass from periodic table
Ex: g NaCl  ? Mole
46.70 g NaCl x =
= mol NaCl
Molar Mass Conversion from PT

4. Converting Mole to Mass
Multiply moles by molar mass conversion
Multiply by molar mass from periodic table
Ex: 5 mol NaCl  ? g NaCl
5 mol NaCl x =
= g NaCl
Molar Mass Conversion from PT

5. Practice Problems If given grams, convert to moles
Practice Problems If given grams, convert to moles. If given moles, convert to grams
167.8 g MgOH
19.8 mol MgOH
g KCl
7.3 mol KCl
54.03 g H2O
0.67 mol H2O
78.90 g LiOH
3.42 mol LiOH
100 g Na2S
1.23 mol Na2S

6. Practice Problem Answers
4.06 mol MgOH
g MgOH
2.56 mol KCl
g KCl
3.00 mol H2O
12.07 g H2O
3.29 mol LiOH
81.91 g LiOH
1.28 mol Na2S
96.00 g Na2S

7. Converting Mass to Mass
You will need a balanced equation!
Steps:
Convert Mass to Mole
Convert Moles of Given to Moles of Wanted
Use mole conversion factor from balanced equation.
Convert Mole to Mass

8. Guided Practice
How many grams of NaCl are produced from the synthesis of sodium and chlorine if g Na were used?
Na + Cl2  2NaCl
g Na x = 4.60 mol Na
4.60 mol Na x = 9.20 mol NaCl
9.20 mol NaCl x = g NaCl

9. Dimensional Analysis
From Equation
From PT
From PT

10. Mass to Mass Practice Problems
How many grams of H2 were used to make 95.0 g H2O in a synthesis reaction?
If 70.9 grams of chlorine gas reacts completely with MgBr2 how many grams of MgCl2 are produced?
When 189 grams of HCl reacts with NaOH, how many grams of water are produced?
If g potassium sulfide is decomposed, how many grams of potassium will be produced?
When calcium and chlorine react, 500 g of calcium chloride is produced. How many grams of calcium were needed in this reaction?

11. Mass-Mass Practice Answers
10.64 g H2
95.21 g MgCl2
93.41 g H2O
63.34 g K
g CaCl2

12. Mole Island Map Mole Island Mainland Mass Particle Paradise
(g)
PT Parkway (molar mass)
Mole Island
(mol)
÷ 22.4 L
Good Ship STP
Particle Paradise
Volcano o’ Volume
(L)
x 22.4L

13. Converting between Moles and Volume
Moles of a gas can be converted to liters (volume) when the gas is at standard temperature and pressure (STP)
STP is 0° C and kPa ( or 1 atm)
At STP, 1 mole of any gas occupies a volume of 22.4 L (molar volume of gas)

14. Guided Practice
How many liters of H2 are present in 3.40 mol H2 at STP?
3.40 mol H2 x = L H2
2. At STP, how many moles of water vapor are present in 90 L of H2O?
90 L H2O x = 4.02 mol H2O

15. Practice Problems If given moles, convert to liters
Practice Problems If given moles, convert to liters. If given liters, convert to moles. Assume all are at STP.
0.60 mol SO2
78.9 L SO2
3.20 x 10-3 mol CO2
190.7 L CO2
16.45 L N2
3.20 mol N2
45.99 L H2
8.9 mol H2
44.8 L CO
1.23 mol CO

16. Mole Island Map Mole Island Mainland Mass Particle Paradise
(g)
PT Parkway (molar mass)
Mole Island
(mol)
÷ (6.02 x 1023)
÷ 22.4 L
Good Ship STP
Avogadro
Airways
Particle Paradise
(particles)
Volcano o’ Volume
(L)
x 22.4L
x (6.02 x 1023)

17. Converting Moles to Particles
Particles can be any type of matter (molecules, atoms, formula units, etc.)
In any given substance, 1 mole = 6.02 x 1023 particles
6.02 x 1023 is called Avogadro’s Number

18. Guided Practice
How many moles of chlorine exist if it has 9.03 x 1023 atoms?
9.03 x 1023 atoms Cl x = 1.51 mol Cl
How many molecules make up 3.2 mol CO2 ?
3.2 mol CO2 x = 1.93 x 1024 molecules CO2

19. Practice Problems If given particles, convert to moles
Practice Problems If given particles, convert to moles. If given moles, convert to particles.
8.09 x 1023 atoms O2
16.23 x 1035 particles Cl2
7.83 x 1014 molecules CO
4.23 x 1023 atoms SO2
6.02 x 1023 formula units H2O
2.3 mol O2
1.4 mol Cl2
190 mol CO
3.429 mol SO2
1.5 mol H2O

20. Practice Problems Answers
1.34 mol O2
2.70 x 1012 mol Cl2
1.00 x mol CO
0.70 mol SO2
1.00 mol H2O
1.38 x particles O2
8.43 x particles Cl2
1.14 x 1026 particles CO
2.06 x 1024 particles SO2
9.03 x particles H2O

21. 3 step Problem Set-Up
Convert to Mol Mole Ratio Convert from mol Given x x x

22. 3 step Guided Problems
How many liters of O2 are used to create 4.56 x 1024 molecules of water?
O2 + 2H2  2H2O
2. How many grams of methane are used to produced 34.8 L of CO2?
CH4 + 2O2  CO2 + 2H2O

23. Particles (atoms/molecules)= 6.02 x 1023
Volume (liters) = 22.4
Mass (grams) = molar mass from Periodic Table

24. Think about making grilled cheese…
To make a good grilled cheese sandwich, you would need two pieces of bread, 2 pieces of cheese, and 1 pat of butter. Write an equation that describes making a grilled cheese sandwich.
If you had 6 pieces of bread, 4 pieces of cheese, and 3 pats of butter, which of the ingredients would limit how many sandwiches could be made?
Which of the ingredients would be leftover?

25. Limiting and Excess Reagent
Limiting Reagent: reactant that determines the amount of product that can be formed
The reaction only occurs until the limiting reagent is used up
Excess Reagent: the reactant that is not completely used up
Some of the reactant is leftover after the reaction occurs

26. How to solve limiting and excess reagent problems
You will be given 2 starting points, so you will solve 2 stoichiometry problems.
Ex: Copper reacts with sulfur to form copper(I) sulfide. Identify the limiting and excess reagents when 80.0 g Cu reacts with 25.0 g S.
2Cu + S  Cu2S
80.0 g Cu x x x =
25.0 g S x x x =
Limiting=Cu, Excess=S, Amount produced = g Cu2S
g Cu2S
gCu2S

27. Practice Problems For each problem, indicate the limiting reagent, the excess reagent, and the amount produced.
1. The combustion of ethene is described below:
C2H4 + 3O2  2CO2 + 2H2O
If 2.70 mol C2H4 is reacted with 6.30 mol O2, identify the limiting reagent.
2. When 6.00 g HCl reacts with 5.00 g Mg, how many grams of hydrogen gas can be produced?
2HCl + Mg  MgCl2 + H2

28. Percent Yield = Actual Yield/Theoretical Yield (100)
Theoretical Yield = what you could get according to stoichiometry
Actual Yield = what is really made in the lab (usually lower than theoretical due to error/loss of efficiency in system)
Percent Yield = Actual Yield/Theoretical Yield (100)