1. CHAPTER 11
Stoichiometry
11.1 Analyzing a Chemical Reaction

2. Chemical equations tell stories…
2CO(g) + O2(g) → 2CO2(g)

3. Chemical equations tell stories…
2CO(g) + O2(g) → 2CO2(g)
… and stories can be put into different categories
Nonfiction
Science fiction
Adventure
Romance
History
Psychology
Children’s literature …

4. Chemical equations tell stories…
2CO(g) + O2(g) → 2CO2(g)
… and stories can be put into different categories
Nonfiction
Science fiction
Adventure
Romance
History
Psychology
Children’s literature …
Synthesis / Decomposition
Single / Double replacement
Precipitate reaction
Polymerization reaction

5. Synthesis / Decomposition
Chemical equations tell stories…
2CO(g) + O2(g) → 2CO2(g)
… and stories can be put into different categories
Synthesis / Decomposition
Single / Double replacement
Precipitate reaction
Polymerization reaction

6. 2CO(g) + O2(g) 2CO2(g) Chemical equations tell stories…
But what exactly do they tell us?
2CO(g) O2(g) CO2(g)

7. 2CO(g) + O2(g) 2CO2(g) Chemical equations tell stories…
But what exactly do they tell us?
2CO(g) O2(g) CO2(g)
They tell us what compounds we start with:
Carbon monoxide (CO) gas
Oxygen (O2) gas

8. 2CO(g) + O2(g) 2CO2(g) Chemical equations tell stories…
But what exactly do they tell us?
2CO(g) O2(g) CO2(g)
They tell us what compounds we start with:
Carbon monoxide (CO) gas
Oxygen (O2) gas
what compounds are formed:
Carbon dioxide (CO2) gas

9. 2CO(g) + O2(g) 2CO2(g) Chemical equations tell stories…
What else do they tell us?
2CO(g) O2(g) CO2(g)

10. They tell us how much of each compound is involved
Chemical equations tell stories…
What else do they tell us?
2CO(g) O2(g) CO2(g)
2 CO molecules
1 O2 molecules
2 CO2 molecules
They tell us how much of each compound is involved

11. They tell us how much of each compound is involved
Chemical equations tell stories…
What else do they tell us?
2CO(g) O2(g) CO2(g)
2 CO molecules
1 O2 molecules
2 CO2 molecules
They tell us how much of each compound is involved
stoichiometry: the study of the amounts of substances involved in a chemical reaction.

12. 2CO(g) + O2(g) 2CO2(g) 2 CO molecules 2 dozen CO molecules
1 dozen O2 molecules

13. 2CO(g) + O2(g) 2CO2(g) 2 CO molecules 2 dozen CO molecules
2 moles CO molecules
2 CO2 molecules
2 dozen CO2 molecules
2 moles CO2 molecules
1 O2 molecules
1 dozen O2 molecules
1 mole O2 molecules

14. 2CO(g) + O2(g) 2CO2(g) 2 CO molecules 2 dozen CO molecules
2 moles CO molecules
2 x (6.023 x 1023) CO molecules
2 CO2 molecules
2 dozen CO2 molecules
2 moles CO2 molecules
2 x (6.023 x 1023) CO2 molecules
1 O2 molecules
1 dozen O2 molecules
1 mole O2 molecules
(1 x) x 1023 O2 molecules

15. Number of moles is not conserved
Is that okay?
2CO(g) O2(g) CO2(g)
Number of moles is not conserved
2 moles
CO molecules +
1 mole
O2 molecules ≠
2 moles
CO2 molecules

16. Number of moles is not conserved
Is that okay?
Yes,
as long as the chemical equation is balanced!
2CO(g) O2(g) CO2(g)
Number of moles is not conserved
2 moles
CO molecules +
1 mole
O2 molecules ≠
2 moles
CO2 molecules

17. 2CO(g) + O2(g) 2CO2(g) = + = This chemical equation is balanced
2 C atoms
2 O atoms
2 O atoms
2 C atoms
4 O atoms
Number of atoms is conserved = + =
2CO(g) O2(g) CO2(g)
This chemical equation is balanced

18. 2CO(g) + O2(g) 2CO2(g) This chemical equation is balanced
Coefficients
2CO(g) O2(g) CO2(g)
2 moles
CO molecules
1 mole
O2 molecules
2 moles
CO2 molecules
This chemical equation is balanced
The coefficients are correct

19. 2CO(g) + O2(g) 2CO2(g) These are important!
Coefficients
2CO(g) O2(g) CO2(g)
2 moles
CO molecules
1 mole
O2 molecules
2 moles
CO2 molecules
This chemical equation is balanced
The coefficients are correct

20. Coefficients are important
1 bag
cake mix
+ 3 eggs + ¼ cup oil cup water batch cupcakes

21. Coefficients are important
1 bag
cake mix
+ 3 eggs + ¼ cup oil cup water batch cupcakes
I need ¼ cup of oil to make 1 batch of cupcakes

22. Coefficients are important
1 bag
cake mix
+ 3 eggs + ¼ cup oil cup water batch cupcakes
Write as a ratio:

23. Coefficients are important
1 bag
cake mix
+ 3 eggs + ¼ cup oil cup water batch cupcakes
I need 1 cup of oil to make 4 batches of cupcakes

24. Coefficients are important
1 bag
cake mix
+ 3 eggs + ¼ cup oil cup water batch cupcakes
Write as a ratio:

25. Coefficients are important
Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)

26. Coefficients are important
Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide

27. Coefficients are important
Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
1 moles
3 moles
2 moles
6 moles
ethanol/
carbon dioxide
x 3
glucose will yield

28. Coefficients are important
Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
1 moles
3 moles
7.5 moles
2 moles
6 moles
15 moles
x 3
ethanol/
carbon dioxide
x 7.5
glucose will yield

29. You MUST multiply all the coefficients by the same number
Coefficients are important
Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
You MUST multiply all the coefficients by the same number
7.5C6H12O6(aq) C2H5OH(aq) CO2(g)
7.5 moles
glucose
15 moles
ethanol
15 moles
carbon dioxide

30. These are stoichiometric equivalents
Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
Write as a ratio:
These are stoichiometric equivalents

31. Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
Write as a ratio:
mole ratio: a ratio comparison between substances in a balanced equation. It is obtained from the coefficients in the balanced equation.

32. Mole ratios Fermentation of sugar (glucose) into alcohol:
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
mole ratios for this chemical equation
11.1 Analyzing a Chemical Reaction

33. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
Compare the reactant CO to the product CH3OH.

34. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
Compare the reactant CO to the product CH3OH.

35. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
If the reaction produces 5 moles of CH3OH, how many moles of H2 are consumed?

36. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
If the reaction produces 5 moles of CH3OH, how many moles of H2 are consumed?
Asked: moles of H2
Given: moles of CH3OH

37. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
If the reaction produces 5 moles of CH3OH, how many moles of H2 are consumed?
Write the mole ratio
between H2 and CH3OH
Write moles of H2 (asked) “on top”
Asked: moles of H2
Given: moles of CH3OH

38. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
If the reaction produces 5 moles of CH3OH, how many moles of H2 are consumed?
Write the mole ratio
between H2 and CH3OH
Write moles of H2 (asked) “on top”
Asked: moles of H2
“on top”

39. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
If the reaction produces 5 moles of CH3OH, how many moles of H2 are consumed?
Given: moles of CH3OH

40. Mole ratios Consider the following equation: CO(g) + 2H2(g) CH3OH(l)
carbon monoxide
hydrogen
methanol
If the reaction produces 5 moles of CH3OH, how many moles of H2 are consumed?
Asked: moles of H2

41. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?

42. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2

43. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2
Write the mole ratio
between AlCl3 and Cl3
Write moles of AlCl3 (asked) “on top”

44. Write moles of AlCl3 (asked) “on top”
A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2
Write the mole ratio
between AlCl3 and Cl3
Write moles of AlCl3 (asked) “on top”
“on top”

45. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2

46. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2
units cancel out

47. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2
units cancel out

48. A mixture of aluminum metal and chlorine gas reacts to form aluminum chloride (AlCl3): 2Al(s) + 3Cl2(g) → 2AlCl3(s). How many moles of aluminum chloride will form when 5 moles of chlorine gas react with excess aluminum metal?
Asked: moles AlCl3
Given: moles Cl2
Answer: 3.3 moles of AlCl3 are produced.

49. There is no scale that measures in moles!
How do you convert from moles to grams?
The mass of 1 mole of Al is not the same as the mass of 1 mole of Cl2.
How do you convert from grams of Al to grams of Cl2?

50. There is no scale that measures in moles!
How do you convert from moles to grams?
By using the molar mass (g/mole)
The mass of 1 mole of Al is not the same as the mass of 1 mole of Cl2.
How do you convert from grams of Al to grams of Cl2?
By using the molar mass (g/mole) and mole ratios

51. Process for calculating grams from grams given

52. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Calcium carbonate (CaCO3) is present in rocks, eggshells and most seashells.
CaCO3 decomposes when it is heated.

53. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships:
mole ratios
molar mass of CaCO3 = ( x 3) = g/mole
molar mass of CO2 = ( x 2) = g/mole
Strategy:

54. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
45.0 g CaCO3

55. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
45.0 g CaCO moles CaCO3

56. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
0.45 moles CaCO3

57. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
0.45 moles CaCO moles CO2

58. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
0.45 moles CO2

59. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
0.45 moles CO g CO2

60. If 45.0 g of calcium carbonate (CaCO3) decomposes in the reaction CaCO3(s) → CaO(s) + CO2(g), how many grams of CO2 are produced?
Asked: grams of CO2 Given: grams of CaCO3
Relationships: mole ratios, molar mass of CaCO3 = g/mole
molar mass of CO2 = g/mole
45 g CaCO moles CaCO3
0.45 moles CO g CO2
Answer: 19.8 g of CO2 are produced.

61. These are stoichiometric equivalents
C6H12O6(aq) C2H5OH(aq) + 2CO2(g)
1 mole
glucose
2 moles
ethanol
2 moles
carbon dioxide
Mole ratios:
These are stoichiometric equivalents