1. Chapter 12--Stoichiometry
12.1 The Arithmetic of Equations interpreting chemical equations and mass conservation in chemical reactions
12.2 Chemical Calculations mole ratios (mole-mole; mass-mass; general dimensional anaylsis)
12.3 Limiting Reagent and Percent Yield know definitions of limiting and excess reagents only; percent yield
What is stoichiometry?         It's not just a funny word--> Stoichiometry is  a very important, useful and mathy part of chemistry. Stoichiometry deals with calculations about the masses (sometimes volumes) of reactants and products involved in a chemical reaction. If you understand how it works, it really isn't that hard. Stoichiometry allows a chemist or scientist to know how much of an element or reactant to use, how much product is expected to come out of the reaction, and how to express different amounts of a substance in many units of measurement. So get ready, get set, and get excited to start learning about stoichiometry!

2. Guided Notes 2. Define stoichiometry.
1. Write the key concept on p. 354.
2. Define stoichiometry.
3. Write the key concept on p. 356.
4. What does a chemical equation tell you about the following quantities (p )?
number of atoms:
number of molecules:
moles:
mass:
volume:
5. Write the key concept AND the sentence following the key concept on p. 357.
6. Define mole ratio.
7. Write the equation on p. 359 and the mole ratios shown.
8. Write the key concept on p. 359.
9. Read and write sample problem 12.2 on p. 360.
10. (p. 360) Given ,
write 6 mole ratios that can be derived from this equation:
how many moles of aluminum are needed to form 3.7 mole Al2O3?

3. Guided Notes continued
11. Read and write sample problem 12.3 on p. 361.
(p. 361) Given
(acetylene gas and calcium carbide), how many grams of acetylene are produced by adding water to 5.00 g CaC2?
13. Read and write sample problem 12.4 on p. 364.
(p. 364) Given
how many molecules of oxygen are produced by the decomposition of 6.54 g of potassium chlorate?
15. Read and write sample problem 12.5 on p. 365.
(p. 365) Given
how many liters of oxygen are required to burn 3.86 L of carbon monoxide?
17. Define theoretical, actual, and percent yield.
18. Write the key concept on p. 373.
(p. 374) Given
what is the theoretical yield when 84.8 g of iron (III) oxide reacts with an excess of carbon monoxide?

4. 12.1 The Arithmetic of Equations
More than 3000 cocoons are needed to produce enough silk to make just one elegant Japanese kimono. Like silk manufacturers, chemists must know how much reactant they need to make a certain amount of product. Determining the quantities of reactants and products in a reaction requires a balanced chemical equation.

5. Using Everyday Equations
12.1
Using Everyday Equations
An equation can represent the manufacturing of a single tricycle.

6. Using Balanced Chemical Equations
12.1
Using Balanced Chemical Equations
How do chemists use balanced chemical equations?
Chemists use balanced chemical equations as a basis to calculate how much reactant is needed or product is formed in a reaction.
The calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry.

7. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
In terms of what quantities can you interpret a balanced chemical equation?
A balanced chemical equation can be interpreted in terms of different quantities, including numbers of atoms, molecules, or moles; mass; and volume.

8. We can describe in terms of number of atoms, molecules, or moles
We can also describe in terms of mass and volume
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

9. Mass Conservation in Chemical Reactions
12.1
Mass Conservation in Chemical Reactions
What quantities are conserved in every chemical reaction?
mass and number of atoms

11. 2 H2S + 3 O2  2 SO2 + 2 H2O
Interpret this equation terms of
b. masses of reactants and products
mass of reactants = mass of products

12. 2 C2H2 (g) + 5 O2 (g)  4 CO2 (g) + 2 H2O (g)
Moles:
Volume:
Mass:
Number of moles is not conserved
Volume is not conserved (7 moles vs. 6 moles of gas x 22.4 L/mol)
Mass is conserved
Atoms are conserved so the reactants 52 g g = products 176g + 36 g = 212 g

13. 12.1 Section Quiz
1. A manufacturer of bicycles has 5350 wheels, 3023 frames, and 2655 handlebars. How many bicycles can be manufactured using these parts?
a) 2675 bicycles
b) 2655 bicycles
c) 3023 bicycles
d) 5350 bicycles

14. 12.1 Section Quiz
2. A reaction that produces iron metal from iron ore is shown below.
Fe2O3•H2O(s) + 3CO(g)  2Fe(s) + 3CO2(g) + H2O(g)
In this equation, the volume of gas at STP that reacts and the volume of gas at STP produced will be
a) 3 L and 4 L.
b) L and 89.6 L.
c) L and 67.2 L
d) 3 L and 3 L

15. 12.2 Chemical Calculations
The effectiveness of car’s air bags is based on the rapid conversion of a small mass of sodium azide into a large volume of gas. The entire reaction occurs in less than a second. You will learn how to use a balanced chemical equation to calculate the amount of product formed in a chemical reaction.

16. Writing and Using Mole Ratios
12.2
Mole-Mole Calculations
A mole ratio is a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles.
Mole ratios are used to convert between moles of reactant and moles of product, between moles of reactants, or between moles of products.

17. Writing and Using Mole Ratios
12.2
To determine the number of moles in a sample of a compound, first measure the mass of the sample. Then use the molar mass to calculate the number of moles in that mass
To determine the number of moles in a sample of a compound, first measure the mass of the sample. Then use the molar mass to calculate the number of moles in that mass.

18. 1 mol nitrogen reacts with 3 mol hydrogen to produce 2 mol ammonia
N2 (g) + 3 H2 (g)  2 NH3 (g)
1 mol nitrogen reacts with 3 mol hydrogen to produce 2 mol ammonia
Manufacturing plants produce ammonia by combining nitrogen with hydrogen. Ammonia is used in cleaning products, fertilizers, and in the manufacture of other chemicals.

19. Writing and Using Mole Ratios
12.2
Writing and Using Mole Ratios
Mass-Mass Calculations

20. Other Stoichiometric Calculations
12.2
What is the general procedure for solving a stoichiometric problem?
In a typical stoichiometric problem, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole, as the problem requires.

21. In this Hubble Space Telescope image, clouds of condensed ammonia are visible covering the surface of Saturn.

22. Other Stoichiometric Calculations
12.2
Solution Diagram
Problem-Solving Approach
This general solution diagram indicates the steps necessary to solve a mass-mass stoichiometry problem: convert mass to moles, use the mole ratio, and then convert moles to mass. Inferring Is the given always a reactant?

23. The electrolysis of water causes it to decompose into hydrogen and oxygen.

26. 12.2 Section Quiz.
1.How many moles of water are produced when 2.5 mol of O2 react according to the following equation?
C3H8 + 5O2  3CO2 + 4H2O
a) 2.0
b) 2.5
c) 3.0
d) 4.0

27. 12.2 Section Quiz
Nitrogen gas reacts with hydrogen gas to produce ammonia gas. N2(g) + 3H2(g)  2NH3(g). What volume of H2 is required to react with 3.00 L of N2, and what volume of NH3 is produced at 200°C?
a) volume of H2 = 9.00 L, volume of NH3 = 6.00 L
b) volume of H2 = 3.00 L, volume of NH3 = 3.00 L
c) volume of H2 = 3.00 L, volume of NH3 = 6.00 L
d) volume of H2 = 1.00 L, volume of NH3 = 1.50 L

28. 12.2 Section Quiz
3. Automotive airbags inflate when sodium azide, NaN3, rapidly decomposes to its component elements via this reaction: 2NaN3  2Na + 3N2. How many grams of sodium azide are required to form 5.00 g of nitrogen gas?
a) g
b) g
c) g
d) g

29. 12.3 Limiting Reagent and Percent Yield
If a carpenter had two tabletops and seven table legs, he could only build one four-legged table. The number of table legs is the limiting factor in the construction of four-legged tables. Similarly, in chemistry, the amount of product made in a chemical reaction may be limited by the amount of one or more of the reactants.

30. Limiting and Excess Reagents
12.3
Limiting and Excess Reagents
How is the amount of product in a reaction affected by an insufficient quantity of any of the reactants?
In a chemical reaction, an insufficient quantity of any of the reactants will limit the amount of product that forms.
The limiting reagent is the reagent that determines the amount of product that can be formed by a reaction.
The reagent that is completely used up is the limiting reagent. The reagent that is not used up is called the excess reagent.

33. Percent Yield What does the percent yield of a reaction measure? 12.3
The percent yield is a measure of the efficiency of a reaction carried out in the laboratory; it is the ratio of the actual yield to the theoretical yield expressed as a percent
(A batting average is actually a percent yield)

34. Percent Yield
12.3
The theoretical yield is the maximum amount of product that could be formed from given amounts of reactants.
In contrast, the amount of product that actually forms when the reaction is carried out in the laboratory is called the actual yield.

37. 12.3 Section Quiz
1.In the reaction 3NO2 + H2O  2HNO3 + NO, how many grams of HNO3 can form when 1.00 g of NO2 and 2.25 g of H2O are allowed to react?
a) g
b) g
c) g
d) g
Limiting reagent problem

38. 12.3 Section Quiz.
2.How many grams of H2O can be formed from 24.0 g O2 and 6.00 g H2?
a) g
b) g
c) g
d) g
Limiting reagent problem

39. 12.3 Section Quiz.
3. Octane burns according to the following equation.
2C8H O2  16CO2 + 18H2O
What is the percent yield if 14.6 g of CO2 are produced when 5.00 g of C8H18 are burned?
a) 106%
b) 94.8%
c) 34.2%
d) 62.5%

40. Write all possible mole ratios for the following chemical equation.
Practice Problems
Write all possible mole ratios for the following chemical equation.
2 HgO (s)  2 Hg (l) + O2 (g)

41. Hydrogen gas can be produced through the following reaction.
Practice Problems
Hydrogen gas can be produced through the following reaction.
Mg (s) + 2 HCl (aq)  MgCl2 (aq) + H2 (g)
What mass of HCl is consumed by the reaction of 2.50 mol of magnesium?

42. Molar Volume of a Gas Lab
Before you began, you determined the amount of zinc needed to produce a specific amount of hydrogen gas. However, the first calculation in the calculations section of the lab, is the theoretical value based on the amount of zinc you actually used.
Assume x = 0.30 g, then your theoretical yield is 103 mL. If your experimental value is 94 mL, then your

43. Ch. 12: What you need to know
12.1
given a chemical equation, know the relationship of reactants and products in terms of atoms, mass, molecules, moles, and volume
know definition of stoichiometry
know conversion factors such as molar mass, molar volume, Avogadro’s number, and mole ratio (carry over from ch. 10)
know that atoms and mass are conserved in a chemical equation (conservation of mass)
12.2
know mole ratios
be able to use mole ratios in calculations (similar to ch. 10)
use ch. 12 worksheet as a guide
12.3
know and be able to calculate theoretical yield, actual yield, and percent yield
Know limiting reagent and excess reagent
know Molar Volume of a Gas and Combustion of Mg Labs
know the chemical equations
know the calculations
review problems assigned from text