1. Stoichiometry
Chapter 11
(page 326)

2. Essential Question!!
Why do scientist compare mole ratios, and why is it important in chemical reactions??

3. Vocabulary: Section 1 Stoichiometry Moles Stoichiometric equivalent
Mole ratio
Gram to gram calculations

4. 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

5. 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.

6. 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

7. 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

8. 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

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

10. 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

11. 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.

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

13. Stoichiometry 1. Mass of substance A 3. Amount in mol of substance B
Convert by dividing by the molar mass of A B
2. Amount in mol of Substance A
Convert using the mol ratio A
Convert by mult. by molar mass of B
4. Mass of Substance B
given in the chemical equation

14. Process for calculating grams from grams given

17. Method Mass - Mass
mass A
mass B =
coeff A X FM A
coeff B X FM B

18. Method Mass - Volume
mass A
vol B =
coeff A * FM A
coeff B * 22.4

19. Method Volume - Volume
vol B
Vol A *
coeff B
coeff A

20. Assignment Take a new sheet of paper and fold it into three sections
Write your name, the title of the chapter and the number
On the first section from the sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

21. 1. Given the equation N2 + 3 H2  2NH3 If 4
1.Given the equation N2 + 3 H2  2NH3 If 4.00 mol of H2 react, how many mol of NH3 will be produced? 2
2.66 mol
4.0 mol X = 3

22. How many moles of sodium will react with water to produce 4
How many moles of sodium will react with water to produce 4.00 mol of Hydrogen? 2 Na + 2H2O  2 NaOH + H2 2
8 mol sodium
4 mol H2 X = 1

23. How many moles of H2SO4 will react with 18. 0 mol of Al
How many moles of H2SO4 will react with 18.0 mol of Al? 2 Al + 3 H2SO4  Al2(SO4)3 + 3 H2 3
18.0 mol Al X =
27.0 moles 2

24. What mass of KClO3 do you need to produce 0. 50 mol of O2
What mass of KClO3 do you need to produce mol of O2? 2 KClO3  2 KCl + 3 O2 2
0.50 mol X
0.33 mol KClO3 = 3
0.33 mol KClO3
X g/mol
= g

25. What mass of Zn metal do you need to produce 0. 50 mol of ZnCl2
What mass of Zn metal do you need to produce mol of ZnCl2? Zn (s) + 2HCl  ZnCl2(s) + H2(g) 1
0.50 mol X
0.5 Zn = 1
0.5 mol Zn
X g/mol
= 32.7 g Zn

26. What mass of NH3 do you need to produce 0. 25 mol of H2
What mass of NH3 do you need to produce mol of H2? N2 + 3H2(g)  2 NH3 3
0.25 mol X
0.375 H2 = 2
0.375 mol H2
X g/mol
= 0.75 g H2

27. Assignment
Write a three dollar summary of this section (based on what you learned) and using three vocabulary words learned
Answer questions # 1- 3 on page 360
Turn in completed work
Honors Chemistry Homework:
Page 362 #

28. Vocabulary: Section 2
Percent yield
Actual yield
Theoretical yield

29. + In theory, all 100 kernels should have popped.
Did you do something wrong? +
100 kernels
82 popped
18 unpopped

30. Percent yield
What you get to eat! +
100 kernels
82 popped
18 unpopped

31. actual yield: the amount obtained in the lab in an actual experiment.
theoretical yield: the expected amount produced if everything reacted completely.

32. Percent yield in the lab
Decomposition of baking soda:
2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g)
10.00 g
4.87 g
measured experimentally
Can you think of reasons why the final mass of Na2CO3 may not be accurate? (What could be sources of error?)
- There is usually some human error, like not measuring exact amounts carefully
- Maybe the heating time was not long enough; not all the Na2HCO3 reacted
- Maybe Na2CO3 was not completely dry; some H2O(l) was measured too
- CO2 is a gas and does not get measured

33. Percent yield in the lab
Decomposition of baking soda:
2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g)
10.00 g
4.87 g
measured experimentally
Let’s calculate the percent yield
obtained in experiment
calculated

34. Conversions of Mass to Amounts In Moles
Example

36. Mass to Mass Calculations
Example

38. Assignment
Write a three dollar summary of this section (based on what you learned)
Answer questions # 4- 6 on page 360
Turn in completed work
Honors Chemistry Homework
Page 363 #

39. Vocabulary: 3
Limiting reactant
Excess reactant

40. Recipe: Suppose you want to make 2 ham & cheese sandwiches
4 slices of bread
4 slices of ham
2 slices of cheese

41. No, you are limited by the cheese!
Suppose you want to make 2 ham & cheese sandwiches
Can you still make 2 ham & cheese sandwiches if you have
4 slices of bread, 4 slices of ham, and 1 slice of cheese?
Limiting factor
No, you are limited by the cheese!
You can only get 1 ham & cheese sandwich.

42. Limiting Reactants
A limiting reactant is the reactant that limits the amount of the other reactants that can combine to form product in a chemical reaction
An excess reactant is the reactant that is left over after the other reactant runs out, or the reaction is completed

43. For a chemical reaction:
Reactant A is in excess
so the reaction will stop when you run out of reactant B.
Reactant B is the limiting reactant.
The amount of product C will depend on how much reactant B
is present.
Excess reactant

44. Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s)
1. What is the limiting reactant?
150 g
60 g
Step 1: Convert masses to moles
Step 2: Use mole ratios to find the limiting reactant

45. Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s)
1. What is the limiting reactant?
150 g
60 g
Step 1: Convert masses to moles
available Fe2O3
available Al
Step 2: Use mole ratios to find the limiting reactant
needed to react with all Fe2O3
needed to react with all Al

46. Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s)
1. What is the limiting reactant?
150 g
60 g
Step 1: Convert masses to moles
available Fe2O3
available Al
Step 2: Use mole ratios to find the limiting reactant
needed to react with all Fe2O3
needed to react with all Al

47. Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s)
1. What is the limiting reactant?
150 g
60 g
available Fe2O3
There is not enough Fe2O3 available to react with all the Al, so Fe2O3 is the limiting reactant
needed to react with all Al

49. Example # 1 & 2

50. The Haber-Bosch process for the synthesis of ammonia:
N2(g) + 3H2(g) → 2NH3(s)

51. The Haber-Bosch process for the synthesis of ammonia:
N2(g) + 3H2(g) → 2NH3(s)

52. Vocabulary: Section 4
Excess reactant
Percent yield

55. What is left? 6Li(s) + N2(g) → 2Li3N(s)
Lithium metal (Li) reacts directly with nitrogen gas (N2) to produce lithium nitride (Li3N) according to the reaction:
6Li(s) + N2(g) → 2Li3N(s)
Asked: Amount of excess reactant left
Given: N2 is the excess reactant
1.15 moles N2 (need)
1.66 moles N2 (have)
Relationships:
28.01 g/mole N2
Solve: 1) How many moles N2 remain?
2) Convert moles to grams
Answer: 14 g of N2 will remain at the end of the reaction.

56. Reactants in solution CuSO4(aq) + Na2S(aq) → Na2SO4(aq) + CuS(s)
The concentration of Cu2+ ions [found as CuSO4(aq)] in the water discharged from an industrial plant is found by adding an excess of sodium sulfide (Na2S) solution to 1.0 L of the contaminated water. The reaction is:
CuSO4(aq) + Na2S(aq) → Na2SO4(aq) + CuS(s)
Asked: Concentration of CuSO4(aq)
Given: 1.0 L of solution is tested
0.021 g CuS (formed)
Relationships:
95.61 g/mole CuS
1 mole CuSO4 ~ 1 mole CuS
Solve: 1) How many moles of CuS?
2) How many moles of CuSO4?
3) What is the concentration of CuSO4?
Have:

57. Assignment
On the second section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

58. Percent Yield
Theoretical yield is the maximum amount of product that can be produced from a given amount of reactant
Actual yield is the measured amount of product obtained from a reaction
Percent yield is the ratio of the actual yield to the theoretical yield

60. Assignment
Write a three dollar summary of this section (based on what you learned) and using the vocabulary learned this section
Answer questions # 7- 8 on page 360
Turn in completed work
Honors Chemistry Homework
Page 364 #

61. Test:- Next Tuesday or Thursday depending on your class
Homework requirement: page 360 # 1 - 8
Make sure you have all work assigned between pages 360 and 363 completed and turned in by your test date.