Document 2517743

05_Chem_GRSW_Ch12.SE/TE 6/11/04 3:45 PM Page 127
Name ___________________________
12
Date ___________________
Class __________________
STOICHIOMETRY
SECTION 12.1 THE ARITHMETIC OF EQUATIONS (pages 353–358)
This section explains how to calculate the amount of reactants required or
product formed in a nonchemical process. It teaches you how to interpret
chemical equations in terms of interacting moles, representative particles,
masses, and gas volume at STP.
Using Everyday Equations (pages 353–355)
1. How can you determine the quantities of reactants and products in a chemical
reaction?
You can use the balanced equation.
amount
2. Quantity usually means the ______________________
of a substance expressed
in grams or moles.
3. A bookcase is to be built from 3 shelves (Sh), 2 side boards (Sb), 1 top (T), 1
base (B), and 4 legs (L). Write a “balanced equation” for the construction of
this bookcase.
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3Sh 2Sb T B 4L Sh3Sb2TBL4
Using Balanced Chemical Equations (page 354)
4. Is the following sentence true or false? Stoichiometry is the calculation of
true
quantities in chemical reactions. ______________________
stoichiometric calculations
5. Calculations using balanced equations are called __________________________.
Interpreting Chemical Equations (pages 356–357)
6. From what elements is ammonia produced? How is it used?
Ammonia molecules are composed of nitrogen and hydrogen; it is used as a fertilizer.
7. Circle the letter of the term that tells what kind of information you CANNOT
get from a chemical equation.
a. moles
d. volume
b. mass
e. number of particles
c. size of particles
Chapter 12 Stoichiometry 127
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Name ___________________________
Date ___________________
Class __________________
CHAPTER 12, Stoichiometry (continued)
8. The coefficients of a balanced chemical equation tell you the relative number of
reactants
products
moles of ______________________
and ______________________
in a chemical reaction.
9. Why is the relative number of moles of reactants and products the most
important information that a balanced chemical equation provides?
Knowing the relative number of moles allows you to calculate the amounts of
reactants and products.
Mass Conservation in Chemical Reactions (pages 357–358)
10. Is the following sentence true or false? A balanced chemical equation must
true
obey the law of conservation of mass. ______________________
11. Use Figure 12.3 on page 357. Complete the table about the reaction of nitrogen
and hydrogen.
N2(g)
2
atoms N
1 molecule N2
(6.02 1023
molecules N2)
1
3H2(g)
L 2NH3(g)
6 atoms H
L
3
L
3 (6.02 1023
molecules H2)
28 g N2
3
34
mol H2
2
L
atoms N and
2
molecules NH3
2
(6.02 1023
molecules NH3)
6
L 2 mol NH3
g H2
g reactants
L 2
17
g NH3
L 34 g products
67.2 L H2
L
44.8 L NH3
12. Circle the letter(s) of the items that are ALWAYS conserved in every chemical
reaction.
a. volume of gases
d. moles
b. mass
e. molecules
c. formula units
f. atoms
13. What reactant combines with oxygen to form sulfur dioxide? Where can this
reactant be found in nature?
Hydrogen sulfide gas combines with oxygen to form sulfur dioxide. It can be found in
volcanic areas.
128 Guided Reading and Study Workbook
atoms H
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3
1 mol N2
Assume STP
22.4 L N2
molecules H2
2
05_Chem_GRSW_Ch12.SE/TE 6/11/04 3:45 PM Page 129
Name ___________________________
Date ___________________
Class __________________
SECTION 12.2 CHEMICAL CALCULATIONS (pages 359–366)
This section shows you how to construct mole ratios from balanced chemical
equations. It then teaches you how to calculate stoichiometric quantities from
balanced chemical equations using units of moles, mass, representative
particles, and volumes of gases at STP.
Writing and Using Mole Ratios (pages 359–362)
1. What is essential for all calculations involving amounts of reactants and
A balanced chemical equation is essential.
products? ___________________________________________________________________
2. Is the following sentence true or false? If you know the number of moles
of one substance in a reaction, you need more information than the
balanced chemical equation to determine the number of moles of all the
other substances in the reaction.
false
______________________
3. The coefficients from a balanced chemical equation are used to write
mole ratios
conversion factors called ______________________
.
4. What are mole ratios used for?
Mole ratios are used to calculate the number of moles of product from a given
number of moles of reactant or to calculate the number of moles of reactant from
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a given number of moles of product.
5. The equation for the formation of potassium chloride is given by the equation
2K(s) Cl2(g)
2KCl(s)
KL
Write the six possible mole ratios for this equation.
2 mol K
1 mol Cl2
______________________________
1 mol Cl2
2 mol KCl
______________________________
2 mol K
2
mol KCl
______________________________
2 mol KCl
2 mol K
______________________________
1 mol Cl2
2 mol K
______________________________
2 mol KCl
1 mol Cl2
______________________________
6. Is the following sentence true or false? Laboratory balances are used to
false
measure moles of substances directly. ______________________
7. The amount of a substance is usually determined by measuring its mass
grams
in _________________________________________________________________________
.
Chapter 12 Stoichiometry 129
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Name ___________________________
Date ___________________
Class __________________
CHAPTER 12, Stoichiometry (continued)
8. Is the following sentence true or false? If a sample is measured in grams, molar
true
mass can be used to convert the mass to moles. ______________________
9. Complete the flow chart to show the steps for the mass–mass conversion of
any given mass of G to any wanted mass of W . In the chemical equation, a
moles of G react with b moles of W.
1 mol G
mass of G mol G
molar mass G
b mol W
mol G a mol G
mol W mol W
molar mass W
1 mol W
mass W
10. Use the diagram below. Describe the steps needed to solve a mass–mass
stoichiometry problem.
Finally, convert moles of W to mass of W.
aG

→
(given quantity)
mass
of G
1 mol G
mass G
mol G bW
(wanted quantity)
b mol W
a mol G
mol W mass W
1 mol W
mass
of W
Other Stoichiometric Calculations (pages 363–366)
11. Is the following sentence true or false? Stoichiometric calculations can be
expanded to include any unit of measurement that is related to the mole.
true
12. List two or three types of problems that can be solved with stoichiometric calculations.
The problems can include mass–volume, volume–volume, and particle–mass
calculations.
130 Guided Reading and Study Workbook
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First convert mass of G to moles of G. Then use the mole ratio to find moles of W.
05_Chem_GRSW_Ch12.SE/TE 6/11/04 3:45 PM Page 131
Name ___________________________
Date ___________________
Class __________________
13. In any problem relating to stoichiometric calculations, the given quantity is
moles
first converted to ______________________
.
14. The combustion of methane produces carbon dioxide and water. The chemical
equation for this reaction is
CH4(g) 2O2(g)
CO2(g) 2H2O(g)
JKL
Write the three conversion factors you would use to find the volume of carbon
dioxide obtained from 1.5 L of oxygen.
1 mol O2
22.4
L O2
____________________
1 mol CO
2
2 mol O2
____________________
22.4 L CO
2
1 mol CO2
____________________
Reading Skill Practice
Sometimes information you read is easier to remember if you write it in a different format. For
example, the paragraph on page 363 and Figure 12.8 both explain how to solve stoichiometric
problems. Use these explanations to make a diagram or flow chart for solving a particle–mass
stoichiometry problem. Do your work on a separate sheet of paper.
1 mol G
representative
mass W
b mol W
particles of G 6.02 1023 KL mol G a mol G KL mol W 1 mol W mass of W
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SECTION 12.3 LIMITING REAGENT AND PERCENT
YIELD (pages 368–375)
This section helps you identify and use the limiting reagent in a reaction to calculate
the maximum amount of product(s) produced and the amount of excess reagent. It
also explains how to calculate theoretical yield, actual yield, or percent yield, given
appropriate information.
Limiting and Excess Reagents (pages 368–371)
1. What is a limiting reagent? A limiting reagent limits or determines the amount of
product that can be formed in a reaction.
2. Is the following sentence true or false? A chemical reaction stops before the
false
limiting reagent is used up. _____________________
3. Circle the letter of the term that correctly completes the sentence. The reactant
that is not completely used up in a chemical reaction is called the _______ .
a. spectator reagent
c. excess reagent
b. limiting reagent
d. catalyst
Chapter 12 Stoichiometry
131
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Name ___________________________
Date ___________________
Class __________________
CHAPTER 12, Stoichiometry (continued)
4. If the quantities of reactants are given in units other than moles, what is the
first step for determining the amount of product?
a. Determine the amount of product from the given amount of limiting
reagent.
b. Convert each given quantity of reactant to moles.
c. Identify the limiting reagent.
5. In the diagram below, which reactant is the limiting reagent and why? The
chemical equation for the formation of water is 2H2 O2
2H2O.
KL
Hydrogen is the limiting reagent, because three hydrogen molecules will combine
with only three oxygen atoms.
Experimental Conditions
Reactants
Products
Before reaction
2 molecules O2
3 molecules H2
0 molecules H2O
Percent Yield (pages 372–375)
The theoretical yield is the maximum amount of product that could be formed from
given amounts of reactants.
7. The amount of product that actually forms when a chemical reaction is carried
actual
out in a laboratory is called the ______________________
yield.
8. Is the following sentence true or false? The actual yield is usually greater than
false
the theoretical yield. ______________________
9. Complete the equation for the percent yield of a chemical reaction.
actual
yield
Percent yield ____________________ 100%
theoretical yield
10. Describe four factors that may cause percent yields to be less than 100%.
impure reactants, competing side reactions, loss of product during filtration or in
transferring between containers, carelessly measuring reactants or products
132 Guided Reading and Study Workbook
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6. What is the theoretical yield?
05_Chem_GRSW_Ch12.SE/TE 6/11/04 3:45 PM Page 133
Name ___________________________
Date ___________________
Class __________________
GUIDED PRACTICE PROBLEMS
GUIDED PRACTICE PROBLEM 11 (page 360)
11. This equation shows the formation of aluminum oxide.
4Al(s) 3O2(g)
KJKL
2Al2O3(s)
a. How many moles of oxygen are required to react completely with 14.8
moles of aluminum?
Analyze
14.8 mol Al
1. What is the given information? ______________________
moles of O2
2. What is the unknown? ______________________
3 mol O
2
4 mol Al
3. What conversion factor will you need to use? ______________________
Calculate
3 mol O2
mol Al
11.1
4. Complete the solution. 14.8 ____________
____________ ____________
mol O2
4 mol Al
Evaluate
5. Why does the answer have three significant figures?
Because the moles of aluminum is given to three significant figures, and because
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defined numbers such as mole ratios have an infinite number of significant figures.
b. How many moles of aluminum oxide are formed when 0.78 moles of
oxygen react with an excess of aluminum?
Analyze
0.78 mol O2
6. What information is given? ______________________
moles of Al2O3
7. What information is unknown? ______________________
Calculate
2 mol Al2O3
0.78
8. Complete the solution. ____________
mol O2 _______________
3 mol O2
0.52
____________
mol Al2O3
Evaluate
9. Why does the answer have two significant figures?
The answer has two significant figures because the number of moles of oxygen has
two significant figures.
Chapter 12 Stoichiometry 133
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Name ___________________________
Date ___________________
Class __________________
CHAPTER 12, Stoichiometry (continued)
EXTRA PRACTICE (similar to Practice Problem 15, page 364)
15. How many molecules of oxygen are produced by the decomposition of 1225
grams of potassium chlorate (KClO3)?
2KClO3(s)
JKL
2KCl(s) 3O2(g)
1 mol KClO3
3 mol O2
6.02 1023 molecules O2
1225 g KClO3 122.5 g KClO3
2 mol KClO3
1 mol O2
15 6.02 1023 molecules O2 9.03 1024 molecules O2
EXTRA PRACTICE (similar to Practice Problem 17, page 365)
17. The equation for the combustion of carbon monoxide is
2CO(g) O2(g)
2CO2(g)
JKL
How many liters of oxygen are needed to burn 10 liters of carbon monoxide?
22.4 L O2
1 mol CO
1 mol O2
10 L CO 5 L O2
22.4 L CO
2 mol CO
1 mol O2
GUIDED PRACTICE PROBLEM 25 (page 370)
25. The equation for the complete combustion of ethene (C2H4) is
C2H4(g) 3O2(g)
JKL
2CO2(g) 2H2O(g)
Step 1. Calculate the number of
moles of oxygen needed to react
with 2.70 moles of ethane.
Multiply by the mole ratio.
3 mol O2
mol C2H4
2.70 _______________
___________
1 mol C2H4
8.10 mol O2
_______
Step 2. Compare the number of
moles of oxygen needed to the
number given.
6.30 mol O2 given is less than
____________
Step 3. Identify the limiting
reagent.
8.10
Because _________
mol O2 are needed
8.10 mol O2 needed
_______
to react with the 2.70 mol C2H4 and
6.30
only _________
mol O2 are available,
oxygen is the limiting reagent.
___________
134 Guided Reading and Study Workbook
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a. If 2.70 moles of ethene reacted with 6.30 moles of oxygen, identify the
limiting reagent.
05_Chem_GRSW_Ch12.SE/TE 6/11/04 3:45 PM Page 135
Name ___________________________
Date ___________________
Class __________________
b. Calculate the number of moles of water produced.
Step 1. Identify the mole ratio
needed.
2 mol H2O
____________
3 mol O2
Step 2. Calculate the given
number of moles of oxygen.
2 mol H2O
mol O2 ____________
6.30 _________
3 mol O2
4.20
_______ mol H O
2
GUIDED PRACTICE PROBLEM 29 (page 374)
29. When 84.8 grams of iron(III) oxide reacts with an excess of carbon monoxide,
54.3 grams of iron are produced.
Fe2O3(s) 3CO(g)
2Fe(s) 3CO2(g)
JKL
What is the percent yield of this reaction?
Step 1. First calculate the
theoretical yield. Begin by
finding the molar mass of Fe2O3.
55.8 g Fe/mol Fe) 2 mol Fe (_______
16.0 g O3/mol O3)
3 mol O3 (_______
111.6 g 48.0 g
_______
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159.6 g
_______
1 mol Fe2O3
84.8 g Fe2O3 Step 2. Calculate the number of
_______
159.6 g Fe2O3
moles of iron(III) oxide. Multiply by
0.531 mol
the mole/mass conversion factor.
_______
Step 3. Find the number of moles
of Fe expected. Multiply by the
mole ratio.
Step 4. Find the mass of iron that
should be produced. Multiply by
the mole/mass conversion factor.
Step 5. Compare the actual yield
to the theoretical yield by dividing.
Step 6. Write the answer as a
percent, with the correct number
of significant figures.
2 mol Fe
mol Fe2O3 ____________
0.531 ____________
1 mol Fe2O3
1.062 mol Fe
_______
55.8 g Fe
mol Fe
1.062 ____________
____________ 59.3 g Fe
1 mol Fe
54.3 g Fe
actual yield
____________ 0.916
theoretical yield
59.3 g Fe
91.6%
0.916 ____________
Chapter 12 Stoichiometry 135
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Name ___________________________
12
Date ___________________
Class __________________
INTERPRETING GRAPHICS
Use with Section 12.3
Preparation of Salicylic Acid
Student #1
mass of flask
37.820 g
flask C7H6O3
39.961 g
volume of C4H6O3
5.0 mL
mass of watch glass
22.744 g
watch glass C9H8O4
24.489 g
mass of flask
37.979 g
flask C7H6O3
40.010 g
volume of C4H6O3
5.0 mL
mass of watch glass
21.688 g
watch glass C9H8O4
24.197 g
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Student #2
Two students prepared aspirin according to the following reaction in which acetic
anhydride, C4H6O3, reacts with salicylic acid, C7H6O3, to form aspirin, C9H8O4, and
acetic acid, C2H4O2.
C7H6O3 C4H6O3 y C9H8O4 C2H4O2
The procedure involved heating the reaction mixture in a water bath for 15 minutes at
75C, not to exceed 80°C. The mixture was removed from the water bath, and distilled
water was added to decompose any unreacted acetic anhydride. The mixture was then
placed in an ice bath for 5 minutes to facilitate the formation of aspirin crystals. The
aspirin crystals were collected using filtration. The aspirin crystals were dried and
then transferred to a watch glass and massed.
Because their grades were partially based on accuracy, both students used their very
best lab technique. Which student got the better grade and why?
1. Determine the molar masses of the following:
a. acetic anhydride, C4H6O3
b. salicylic acid, C7H6O3
c. aspirin, C9H8O4
Chapter 12 Stoichiometry
297
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Name ___________________________
Date ___________________
Class __________________
2. How many moles of salicylic acid were added to the reaction mixture?
Student 1
Student 2
3. Given the density of acetic anhydride to be 1.05 g/mL, what was the mass of the
acetic anhydride added to the reaction? How many moles of acetic acid were
added?
Student 1
Student 2
4. According to the mole ratios in the given reaction, what is the limiting reagent
in this reaction?
5. What is the theoretical yield, in grams, of aspirin in each reaction?
Student 1
Student 2
6. What was the actual yield, in grams, of aspirin in each reaction?
Student 1
Student 2
7. What was the percent yield in each reaction?
Student 1
Student 2
8. Evaluate your answers. Which student got the better grade and why?
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298
Core Teaching Resources
05_CTR_ch12 7/9/04 3:34 PM Page 295
Name ___________________________
12
Date ___________________
Class __________________
STOICHIOMETRY
Practice Problems
In your notebook, solve the following problems.
SECTION 12.1 THE ARITHMETIC OF EQUATIONS
Use the 3-step problem-solving approach you learned in Chapter 1.
1. An apple pie needs 10 large apples, 2 crusts (top and bottom), and 1 tablespoon
of cinnamon. Write a balanced equation that fits this situation. How many
apples are needed to make 25 pies?
2. Two moles of potassium chloride and three moles of oxygen are produced from
the decomposition of two moles of potassium chlorate, KClO3(s). Write the
balanced equation. How many moles of oxygen are produced from 12 moles of
potassium chlorate?
3. Using the equation from problem 2, how many moles of oxygen are produced
from 14 moles of potassium chlorate?
4. Two molecules of hydrogen react with one molecule of oxygen to produce two
molecules of water. How many molecules of water are produced from 2.0 1023
molecules of oxygen? How many moles of water are produced from 22.5 moles
of oxygen?
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SECTION 12.2 CHEMICAL CALCULATIONS
1. Calculate the number of moles of hydrogen chloride produced from 10 moles of
hydrogen.
H2(g) Cl2(g) y 2HCl(g)
2. Calculate the number of moles of chlorine needed to form 14 moles of iron(III)
chloride.
2Fe(s) 3Cl2(g) y 2FeCl3(s)
3. Calculate the number of grams of nitrogen dioxide that are produced from
4 moles of nitric oxide.
2NO(g) O2(g) y 2NO2(g)
4. Calculate the mass of oxygen produced from the decomposition of 75.0 g of
potassium chlorate.
2KClO3(s) y 2KCl(s) 3O2(g)
5. Calculate the mass of silver needed to react with chlorine to produce 84 g of
silver chloride. (Hint: Write a balanced equation first.)
6. How many liters of carbon monoxide at STP are needed to react with 4.80 g of
oxygen gas to produce carbon dioxide?
2CO(g) O2(g) y 2CO2(g)
7. Calculate the number of liters of oxygen gas needed to produce 15.0 liters of
dinitrogen trioxide. Assume all gases are at the same conditions of temperature
and pressure.
2N2(g) 3O2(g) y 2N2O3(g)
Chapter 12 Stoichiometry
295
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Name ___________________________
Date ___________________
Class __________________
8. A volume of 7.5 L of hydrogen gas at STP was produced from the single-replacement
reaction of zinc with nitric acid. Calculate the mass of zinc needed for this reaction.
SECTION 12.3 LIMITING REAGENT AND PERCENT YIELD
1. How many moles of water can be made from 4 moles of oxygen gas and
16 moles of hydrogen gas? What is the limiting reagent?
2. Calculate the mass of water produced from the reaction of 24.0 g of H2 and
160.0 g of O2. What is the limiting reagent?
3. The burning of 18.0 g of carbon produces 55.0 g of carbon dioxide. What is the
theoretical yield of CO2? Calculate the percent yield of CO2.
4. Calculate the percent yield of Cl2(g) in the electrolytic decomposition of
hydrogen chloride if 25.8 g of HCl produces 13.6 g of chlorine gas.
5. One method for reclaiming silver metal from silver chloride results in a 94.6%
yield. Calculate the actual mass of silver that can be produced in this reaction
if 100.0 g of silver chloride is converted to silver metal.
2AgCl(s) y 2Ag(s) Cl2(g)
6. What is the actual amount of magnesium oxide produced when excess carbon
dioxide reacts with 42.8 g of magnesium metal? The percent yield of MgO(s)for
this reaction is 81.7%.
2Mg(s) CO2(g) y 2MgO(s) C(s)
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Core Teaching Resources
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Name ___________________________
Date ___________________
Class __________________
THE ARITHMETIC OF EQUATIONS
12.1
Section Review
Objectives
• Calculate the amount of reactants required or product formed in a nonchemical
process
• Interpret balanced chemical equations in terms of interacting moles,
representative particles, masses, and gas volume at STP
Vocabulary
• stoichiometry
Part A Completion
Use this completion exercise to check your understanding of the concepts and terms
that are introduced in this section. Each blank can be completed with a term, short
phrase, or number.
The coefficients of a balanced chemical equation indicate
1
the relative number of
of reactants and products. All
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stoichiometric calculations begin with a
and
4
2
. Only
3
are conserved in every reaction; moles, volumes,
and representative particles may not be.
In solving stoichiometric problems, conversion factors
relating moles of reactants to
If you assume
6
5
1.
2.
3.
4.
5.
6.
of products are used.
, the balanced equation also tells you
about the volumes of gases.
Part B True-False
Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 7. The coefficients in a balanced chemical equation can be used to form
mole ratios relating reactants to products.
________ 8. The coefficients in a balanced chemical equation tell the relative
volumes of reactants and products, expressed in any suitable unit of
volume.
________ 9. To calculate the mass of a molecule in grams, you can use the molar
mass and Avogadro’s number.
Chapter 12 Stoichiometry
289
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Name ___________________________
Date ___________________
Class __________________
________ 10. Because the mass of the reactants equals the mass of the products of a
reaction, the number of moles will be conserved.
________ 11. If the ratio of molecules in the reaction 2A2 B2 y 2A2B is 2:1:2, we can
predict that 4 molecules of A2 react with 2 molecules B2 to produce 4
molecules of A2B.
________ 12. One mole of any gas occupies a volume of 22.4 L.
Part C Matching
Match each description in Column B to the correct term in Column A.
Column A
Column B
________ 13. stoichiometry
a. Avogadro’s number
________ 14. product
b. the calculations of quantities in chemical reactions
________ 15. coefficient
c. STP
________ 16. 6.02 1023
d. a substance formed in a chemical reaction
________ 17. 0°C, 101.3 kPa
e. gives the relative number of molecules involved in a
reaction
Part D Questions and Problems
Answer the following in the space provided. Show your work.
19. How many moles of chlorine gas will be required to react with sufficient iron to
produce 14 moles of iron(III) chloride?
2Fe(s) 3Cl2(g) y 2FeCl3(g)
290
Core Teaching Resources
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18. Interpret the following equation using moles, molecules, and volumes (assume
STP). Compare the mass of the reactants to the mass of the product.
2N2(g) 3O2(g) y 2N2O3(g)
05_CTR_ch12 7/9/04 3:34 PM Page 291
Name ___________________________
Date ___________________
Class __________________
CHEMICAL CALCULATIONS
12.2
Section Review
Objectives
• Construct mole ratios from balanced chemical equations and apply these ratios in
mole-mole stoichiometric calculations
• Calculate stoichiometric quantities from balanced chemical equations, using
units of moles, mass, representative particles, and volumes of gases at STP
Key Equations
• mole-mole relationship used in every stoichiometric calculation:
aG uy bW
(given quantity) (wanted quantity)
b mol W
a mol G
xb
a
• x mol G mol W
Given
Mole Ratio
Calculated
Part A Completion
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Use this completion exercise to check your understanding of the concepts and terms
that are introduced in this section. Each blank can be completed with a term, short
phrase, or number.
Mole ratios from balanced equations may be used to solve
2
2.
from the balanced equation are used
3.
problems with other units such as numbers of
of gases at STP. The
3
4
to write conversion factors called
6
and
. These conversion factors
are used to calculate the numbers of moles of
number of moles of
1
1.
5
4.
from a given
5.
. In mass-mass calculations, the molar
6.
mass is used to convert mass to
7
.
7.
Part B True-False
Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 8. In mass-mass calculations, the molar mass is used to convert mass
to moles.
________ 9. The mole ratio 2 mol HF/1 mol SnF2 can be used to determine the
mass of SnF2 produced according to the equation:
Sn(s) 2HF(g) y SnF2(s) H2(g)
Chapter 12 Stoichiometry
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Name ___________________________
Date ___________________
Class __________________
________ 10. In a volume-volume problem, the 22.4 L/mol factors always cancel out.
________ 11. In stoichiometric problems, volume is expressed in terms of liters.
________ 12. For a mass-mole problem, the first conversion from mass to moles
is skipped.
________ 13. For a mass-mass problem, the first conversion is from moles to mass.
________ 14. Because mole ratios from balanced equations are exact numbers, they
do not enter into the determination of significant figures.
Part C Matching
Match each conversion problem in Column A to the correct solution in Column B.
Column A
________ 15. moles O2 y grams O2
________ 16. liters SO2 y grams SO2 at STP
________ 17. molecules He y liters He(g) at STP
________ 18. grams Sn y molecules Sn
________ 19. molecules H2O y grams H2O
Column B
mol
18.0 g
a. molecules 23
6.02 10 molecules
mol
64.1 g
mol
b. liters mol
22.4 L
32.0 g
c. mol mol
mol
22.4 L
d. molecules 6.02 1023molecules
mol
23
6.02 10 molecules
mol
e. grams mol
119 g
Answer the following questions in the space provided.
20. How many liters of carbon monoxide (at STP) are needed to react with 4.8 g of
oxygen gas to produce carbon dioxide?
2CO(g) O2(g) y 2CO2(g)
21. What mass of ammonia, NH3, is necessary to react with 2.1 1024 molecules of
oxygen in the following reaction?
4NH3(g) 7O2(g) y 6H2O(g) 4NO2(g)
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Part D Questions and Problems
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Name ___________________________
Date ___________________
Class __________________
LIMITING REAGENT AND PERCENT YIELD
12.3
Section Review
Objectives
• Identify and use the limiting reagent in a reaction to calculate the maximum
amount of product(s) produced and the amount of excess reagent
• Calculate theoretical yield, actual yield, or percent yield given the appropriate
information
Vocabulary
• limiting reagent
• excess reagent
• theoretical yield
• actual yield
• percent yield
Key Equations
actual yield
theoretical yield
• percent yield 100
Part A Completion
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Use this completion exercise to check your understanding of the concepts and terms
that are introduced in this section. Each blank can be completed with a term, short
phrase, or number.
Whenever quantities of two or more reactants are given in a
1
stoichiometric problem, you must identify the
reagent that is completely
2
1.
. This is the
2.
in the reaction. The amount of
3.
limiting reagent determines the amount of
3
that is formed.
When an equation is used to calculate the amount of product
4
that will form during a reaction, the value obtained is the
This is the
5
.
4.
5.
6.
amount of product that could be formed from a
given amount of reactant. The amount of product that forms when
the reaction is carried out in the laboratory is called the
6
.
Part B True-False
Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 7. Normally, the actual yield in a chemical reaction will be equal to or
less than the theoretical yield.
________ 8. The actual yield of a chemical reaction can be calculated using mole
ratios.
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Name ___________________________
Date ___________________
Class __________________
________ 9. The amount of product can be determined from the amount of excess
reagent.
________ 10. The percent yield of a product is 100 percent.
________ 11. If you had 100 steering wheels, 360 tires, and enough of every other part
needed to assemble a car, the limiting reagent would be tires.
________ 12. The theoretical yield is the maximum amount of product that could
be formed in a chemical reaction.
Part C Matching
Match each description in Column B to the correct term in Column A.
Column A
Column B
a. the ratio of the actual yield to the theoretical yield 100
________ 14. limiting reagent
b. the amount of product actually formed when a reaction is
carried out in the laboratory
________ 15. theoretical yield
c. the reactant that determines the amount of product that can
be formed in a reaction
________ 16. percent yield
d. the reactant that is not completely used up in a chemical
reaction
________ 17. excess reagent
e. the maximum amount of product that can be formed during
a reaction
Part D Questions and Problems
Answer the following in the space provided.
18. a. What is the limiting reagent when 3.1 mol of SO2 react with 2.7 mol of O2
according to the equation:
2SO2(g) O2(g) y 2SO3(g)
b. Calculate the maximum amount of product that can be formed and the
amount of unreacted excess reagent.
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________ 13. actual yield
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Name ___________________________
12
Date ___________________
Class __________________
STOICHIOMETRY
Vocabulary Review
Match the correct vocabulary term to each numbered statement. Write the letter of the
correct term on the line.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Column A
Column B
________ 1. the starting materials in a chemical reaction
a. mole
________ 2. a conversion factor derived from the coefficients of a
balanced chemical equation interpreted in terms of
moles
b. stoichiometry
________ 3. the maximum amount of product that could be
formed in a reaction
c. mass-mass calculation
________ 4. the amount of a substance that contains 6.02 1023
representative particles of that substance
d. reactants
________ 5. the substance completely used up in a chemical
reaction
e. excess reagent
________ 6. the ratio of how much product is produced
compared to how much is expected, expressed as a
percentage
f. theoretical yield
________ 7. the calculations of quantities in a chemical reaction
g. limiting reagent
________ 8. the actual amount of product in a chemical reaction
h. quantity
________ 9. the substance left over after a reaction takes place
i. actual yield
________ 10. a stoichiometric computation in which the mass of
products is determined from the given mass of
reactants
j. percent yield
Chapter 12 Stoichiometry
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Name ___________________________
12
Date ___________________
Class __________________
STOICHIOMETRY
Chapter Quiz
Fill in the word(s) that will make each statement true.
1
1. The
in a balanced chemical equation also reveal the
mole ratios of the substances involved.
1.
12.1
2. The number of moles of a product can be calculated from a
2
given number of moles of
.
2.
12.1
3. In mass-mass calculations, the molar mass is used to
3
convert mass to
.
3.
12.2
4. In addition to mass, the only quantity conserved in every
4
chemical reaction is
.
4.
12.2
5. According to the equation:
2NO(g) O2(g) y 2NO2(g),
5
22.4 L of O2 will react with
L of NO at STP.
5.
12.2
Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
12.3
________ 7. In the reaction 2CO(g) O2(g) y 2CO2(g), using 4 moles of CO to
react with 1 mole of O2 will result in the production of 4 moles of CO2.
12.3
________ 8. To calculate the percent yield of a reaction, you use the following relationship:
theoretical yield
100
actual yield
12.3
________ 9. The total mass of the excess reagent and the limiting reagent is equal
to the total mass of the products.
12.3
________ 10. The actual yield is equal to the theoretical yield.
12.3
300
Core Teaching Resources
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________ 6. The excess reagent determines the amount of product formed in a
reaction.