05 Chem GRSW Ch12.SE/TE · Chapter 12 Stoichiometry129 SECTION 12.2 CHEMICAL CALCULATIONS (pages 359–366) This section shows you how to construct mole ratios from balanced chemical

Chapter 12 Stoichiometry 127

SECTION 12.1 THE ARITHMETIC OF EQUATIONS (pages 353–358)

This section explains how to calculate the amount of reactants required orproduct formed in a nonchemical process. It teaches you how to interpretchemical 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 chemicalreaction?

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), 1base (B), and 4 legs (L). Write a “balanced equation” for the construction ofthis bookcase.

Using Balanced Chemical Equations (page 354)

4. Is the following sentence true or false? Stoichiometry is the calculation of

quantities in chemical reactions. ______________________

5. Calculations using balanced equations are called __________________________.

Interpreting Chemical Equations (pages 356–357)

6. From what elements is ammonia produced? How is it used?

7. Circle the letter of the term that tells what kind of information you CANNOTget from a chemical equation.

a. moles d. volume

b. mass e. number of particles

c. size of particles

Name ___________________________ Date ___________________ Class __________________

STOICHIOMETRY12

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You can use the balanced equation.

amount

stoichiometric calculations

true

3Sh � 2Sb � T � B � 4L � Sh3Sb2TBL4

Ammonia molecules are composed of nitrogen and hydrogen; it is used as a fertilizer.

05_Chem_GRSW_Ch12.SE/TE 6/11/04 3:45 PM Page 127

Name ___________________________ Date ___________________ Class __________________©

Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.

128 Guided Reading and Study Workbook

CHAPTER 12, Stoichiometry (continued)

8. The coefficients of a balanced chemical equation tell you the relative number of

moles of ______________________ and ______________________ in a chemical reaction.

9. Why is the relative number of moles of reactants and products the mostimportant information that a balanced chemical equation provides?

Mass Conservation in Chemical Reactions (pages 357–358)

10. Is the following sentence true or false? A balanced chemical equation must

obey the law of conservation of mass. ______________________

11. Use Figure 12.3 on page 357. Complete the table about the reaction of nitrogenand hydrogen.

12. Circle the letter(s) of the items that are ALWAYS conserved in every chemicalreaction.

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 thisreactant be found in nature?

reactants products

true

Knowing the relative number of moles allows you to calculate the amounts of

reactants and products.

N2(g ) � 3H2(g ) L 2NH3(g )

atoms N � 6 atoms H L atoms N and atoms H

1 molecule N2 � molecules H2 L molecules NH3

� (6.02 � 1023 � 3 � (6.02 � 1023L � (6.02 � 1023

molecules N2) molecules H2) molecules NH3)

1 mol N2 � mol H2 L 2 mol NH3

28 g N2 � 3 � g H2 L 2 � g NH3

g reactants L 34 g products

Assume STP22.4 L N2 � 67.2 L H2 L L NH3

2

1

2

2

2

3

2

34

17

44.8

6

3

Hydrogen sulfide gas combines with oxygen to form sulfur dioxide. It can be found in

volcanic areas.



SECTION 12.2 CHEMICAL CALCULATIONS (pages 359–366)

This section shows you how to construct mole ratios from balanced chemicalequations. It then teaches you how to calculate stoichiometric quantities frombalanced 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

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 theother substances in the reaction.

______________________

3. The coefficients from a balanced chemical equation are used to write

conversion factors called ______________________ .

4. What are mole ratios used for?

5. The equation for the formation of potassium chloride is given by the equation

2K(s) � Cl2(g) KL

2KCl(s)

Write the six possible mole ratios for this equation.

______________________________ ______________________________

______________________________ ______________________________

______________________________ ______________________________

6. Is the following sentence true or false? Laboratory balances are used to

measure moles of substances directly. ______________________

7. The amount of a substance is usually determined by measuring its mass

in _________________________________________________________________________ .

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A balanced chemical equation is essential.

false

mole ratios

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

a given number of moles of product.

2 mol K��1 mol Cl2

1 mol Cl2��2 mol KCl

2 mol KCl��2 mol K

2 mol K��2 mol KCl

1 mol Cl2��2 mol K

2 mol KCl��1 mol Cl2

false

grams



8. Is the following sentence true or false? If a sample is measured in grams, molar

mass can be used to convert the mass to moles. ______________________

9. Complete the flow chart to show the steps for the mass–mass conversion ofany given mass of G to any wanted mass of W . In the chemical equation, amoles of G react with b moles of W.

10. Use the diagram below. Describe the steps needed to solve a mass–massstoichiometry problem.

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.

12. List two or three types of problems that can be solved with stoichiometric calculations.

�massof G mol G � mol W �

massof W

aG

(given quantity)

bW

(wanted quantity)

1 mol Gmass G

b mol Wa mol G

mass W1 mol W

→�


Name ___________________________ Date ___________________ Class __________________©


true

mass of G � � mol G

mol G � �b mol W��a mol G

1 mol G

molar mass G

mol W

mol W �molar mass W

� mass W1 mol W

The problems can include mass–volume, volume–volume, and particle–mass

calculations.

true

First convert mass of G to moles of G. Then use the mole ratio to find moles of W.

Finally, convert moles of W to mass of W.



13. In any problem relating to stoichiometric calculations, the given quantity is

first converted to ______________________ .

14. The combustion of methane produces carbon dioxide and water. The chemicalequation for this reaction is

CH4(g) � 2O2(g)JKL

CO2(g) � 2H2O(g)

Write the three conversion factors you would use to find the volume of carbondioxide obtained from 1.5 L of oxygen.

____________________ ____________________ ____________________

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 calculatethe maximum amount of product(s) produced and the amount of excess reagent. Italso explains how to calculate theoretical yield, actual yield, or percent yield, givenappropriate information.

Limiting and Excess Reagents (pages 368–371)

1. What is a limiting reagent?

2. Is the following sentence true or false? A chemical reaction stops before the

limiting reagent is used up. _____________________

3. Circle the letter of the term that correctly completes the sentence. The reactantthat is not completely used up in a chemical reaction is called the _______ .

a. spectator reagent c. excess reagent

b. limiting reagent d. catalyst

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moles

1 mol CO2��2 mol O2

1 mol O2��22.4 L O2

22.4 L CO2��1 mol CO2

Sometimes information you read is easier to remember if you write it in a different format. Forexample, the paragraph on page 363 and Figure 12.8 both explain how to solve stoichiometricproblems. Use these explanations to make a diagram or flow chart for solving a particle–massstoichiometry problem. Do your work on a separate sheet of paper.

Reading Skill Practice

false

A limiting reagent limits or determines the amount of

product that can be formed in a reaction.

representativeparticles of G �

KLmol G �

KLmol W � � mass of Wmass W

�1 mol Wb mol W�a mol G

1 mol G��6.02 �1023



4. If the quantities of reactants are given in units other than moles, what is thefirst step for determining the amount of product?

a. Determine the amount of product from the given amount of limitingreagent.

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? Thechemical equation for the formation of water is 2H2 � O2 KL

2H2O.

Percent Yield (pages 372–375)

6. What is the theoretical yield?

7. The amount of product that actually forms when a chemical reaction is carried

out in a laboratory is called the ______________________ yield.

8. Is the following sentence true or false? The actual yield is usually greater than

the theoretical yield. ______________________

9. Complete the equation for the percent yield of a chemical reaction.

Percent yield � ____________________ � 100%

10. Describe four factors that may cause percent yields to be less than 100%.

Experimental Conditions

Reactants

3 molecules H2

Products

0 molecules H2O

Before reaction

2 molecules O2


Name ___________________________ Date ___________________ Class __________________©


Hydrogen is the limiting reagent, because three hydrogen molecules will combine

with only three oxygen atoms.

The theoretical yield is the maximum amount of product that could be formed from

given amounts of reactants.

false

actual

theoretical

impure reactants, competing side reactions, loss of product during filtration or in

transferring between containers, carelessly measuring reactants or products

yield

yield

actual



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 14.8moles of aluminum?

Analyze

1. What is the given information? ______________________

2. What is the unknown? ______________________

3. What conversion factor will you need to use? ______________________

Calculate

4. Complete the solution. 14.8 ____________ � ____________ � ____________ mol O2

Evaluate

5. Why does the answer have three significant figures?

b. How many moles of aluminum oxide are formed when 0.78 moles ofoxygen react with an excess of aluminum?

Analyze

6. What information is given? ______________________

7. What information is unknown? ______________________

Calculate

8. Complete the solution. ____________ mol O2 � _______________

� ____________ mol Al2O3

Evaluate

9. Why does the answer have two significant figures?

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14.8 mol Al

mol Al

0.52

11.14 mol Al

moles of O2

3 mol O2�4 mol Al

3 mol O2

Because the moles of aluminum is given to three significant figures, and because

defined numbers such as mole ratios have an infinite number of significant figures.

0.78 mol O2

moles of Al2O3

0.78 mol Al2O32

The answer has two significant figures because the number of moles of oxygen has

two significant figures.

3 mol O2

GUIDED PRACTICE PROBLEMS



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)

EXTRA PRACTICE (similar to Practice Problem 17, page 365)

17. The equation for the combustion of carbon monoxide is

2CO(g) � O2(g) JKL

2CO2(g)

How many liters of oxygen are needed to burn 10 liters of carbon monoxide?


25. The equation for the complete combustion of ethene (C2H4) is

C2H4(g) � 3O2(g) JKL

2CO2(g) � 2H2O(g)

a. If 2.70 moles of ethene reacted with 6.30 moles of oxygen, identify thelimiting reagent.

Step 1. Calculate the number of 2.70 _______________ � ___________

moles of oxygen needed to react with 2.70 moles of ethane. Multiply by the mole ratio. � _______ mol O2

Step 2. Compare the number of ____________ O2 given is less than moles of oxygen needed to the _______ mol O2 needednumber given.

Step 3. Identify the limiting Because _________ mol O2 are neededreagent.

to react with the 2.70 mol C2H4 and

only _________ mol O2 are available,

___________ is the limiting reagent.


Name ___________________________ Date ___________________ Class __________________©


1225 g KClO3 � � �

� 15 � 6.02 � 1023 molecules O2 � 9.03 � 1024 molecules O2

6.02 �1023 molecules O2��1 mol O2

3 mol O2��2 mol KClO3

1 mol KClO3��122.5 g KClO3

10 L CO � � � � 5 L O222.4 L O2��1 mol O2

1 mol O2��2 mol CO

1 mol CO��22.4 L CO

mol O2

1 mol C2H4

mol C2H4

6.30 mol

8.10

3

8.10

8.10

6.30

oxygen



b. Calculate the number of moles of water produced.

Step 1. Identify the mole ratio ____________ needed.

Step 2. Calculate the given 6.30 _________ � ____________

number of moles of oxygen. �_______ mol H2O


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) JKL

2Fe(s) � 3CO2(g)

What is the percent yield of this reaction?

Step 1. First calculate the 2 mol Fe � (_______ g Fe/mol Fe) �theoretical yield. Begin by

3 mol O3 � (_______ g O3/mol O3)finding the molar mass of Fe2O3.

� _______ g � 48.0 g

� _______ g

Step 2. Calculate the number of _______ g Fe2O3 �

moles of iron(III) oxide. Multiply by the mole/mass conversion factor. � _______ mol

Step 3. Find the number of moles 0.531 ____________ � ____________

of Fe expected. Multiply by the mole ratio. � _______ mol Fe

Step 4. Find the mass of iron that 1.062 ____________ � ____________ � 59.3 g Feshould be produced. Multiply by the mole/mass conversion factor.

Step 5. Compare the actual yield � ____________ � 0.916to the theoretical yield by dividing.

Step 6. Write the answer as a 0.916 � ____________percent, with the correct number of significant figures.

actual yield��theoretical yield

1 mol Fe2O3��159.6 g Fe2O3

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mol H2O

mol H2O

3 mol O2

3 mol O2

mol Fe

g Fe

1 mol Fe2O3

1 mol Fe

2

mol O2

4.20

55.8

16.0

111.6

159.6

84.8

0.531

mol Fe2O32

55.8

g Fe

g Fe

54.3

59.3

1.062

mol Fe

91.6%

2



Name ___________________________ Date ___________________ Class __________________

INTERPRETING GRAPHICSUse with Section 12.3

12

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Preparation of Salicylic AcidStudent #1

Student #2

Two students prepared aspirin according to the following reaction in which aceticanhydride, C4H6O3, reacts with salicylic acid, C7H6O3, to form aspirin, C9H8O4, andacetic acid, C2H4O2.

C7H6O3 � C4H6O3y C9H8O4 � C2H4O2

The procedure involved heating the reaction mixture in a water bath for 15 minutes at75�C, not to exceed 80°C. The mixture was removed from the water bath, and distilledwater was added to decompose any unreacted acetic anhydride. The mixture was thenplaced in an ice bath for 5 minutes to facilitate the formation of aspirin crystals. Theaspirin crystals were collected using filtration. The aspirin crystals were dried andthen transferred to a watch glass and massed.

Because their grades were partially based on accuracy, both students used their verybest 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

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

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

05_CTR_ch12 7/9/04 3:34 PM Page 297

298 Core Teaching Resources

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 theacetic anhydride added to the reaction? How many moles of acetic acid wereadded?

Student 1 Student 2

4. According to the mole ratios in the given reaction, what is the limiting reagentin 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?

05_CTR_ch12 7/9/04 3:34 PM Page 298


Name ___________________________ Date ___________________ Class __________________

STOICHIOMETRY12

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Practice ProblemsIn your notebook, solve the following problems.

SECTION 12.1 THE ARITHMETIC OF EQUATIONSUse 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 tablespoonof cinnamon. Write a balanced equation that fits this situation. How manyapples are needed to make 25 pies?

2. Two moles of potassium chloride and three moles of oxygen are produced fromthe decomposition of two moles of potassium chlorate, KClO3(s). Write thebalanced equation. How many moles of oxygen are produced from 12 moles ofpotassium chlorate?

3. Using the equation from problem 2, how many moles of oxygen are producedfrom 14 moles of potassium chlorate?

4. Two molecules of hydrogen react with one molecule of oxygen to produce twomolecules 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 molesof oxygen?

SECTION 12.2 CHEMICAL CALCULATIONS1. 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 ofpotassium chlorate.

2KClO3(s) y 2KCl(s) � 3O2(g)

5. Calculate the mass of silver needed to react with chlorine to produce 84 g ofsilver chloride. (Hint: Write a balanced equation first.)

6. How many liters of carbon monoxide at STP are needed to react with 4.80 g ofoxygen 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 ofdinitrogen trioxide. Assume all gases are at the same conditions of temperatureand pressure.

2N2(g) � 3O2(g) y 2N2O3(g)

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Name ___________________________ Date ___________________ Class __________________©


8. A volume of 7.5 L of hydrogen gas at STP was produced from the single-replacementreaction of zinc with nitric acid. Calculate the mass of zinc needed for this reaction.

SECTION 12.3 LIMITING REAGENT AND PERCENT YIELD1. 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 and160.0 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 thetheoretical yield of CO2? Calculate the percent yield of CO2.

4. Calculate the percent yield of Cl2(g) in the electrolytic decomposition ofhydrogen 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 carbondioxide reacts with 42.8 g of magnesium metal? The percent yield of MgO(s)forthis reaction is 81.7%.

2Mg(s) � CO2(g) y 2MgO(s) � C(s)

05_CTR_ch12 7/9/04 3:34 PM Page 296


Name ___________________________ Date ___________________ Class __________________

THE ARITHMETIC OF EQUATIONS12.1

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Section ReviewObjectives• 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 CompletionUse this completion exercise to check your understanding of the concepts and termsthat are introduced in this section. Each blank can be completed with a term, shortphrase, or number.

The coefficients of a balanced chemical equation indicate 1.

the relative number of of reactants and products. All 2.

stoichiometric calculations begin with a . Only 3.

and are conserved in every reaction; moles, volumes, 4.

and representative particles may not be. 5.

In solving stoichiometric problems, conversion factors 6.

relating moles of reactants to of products are used.

If you assume , the balanced equation also tells you

about the volumes of gases.

Part B True-FalseClassify 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 formmole ratios relating reactants to products.

________ 8. The coefficients in a balanced chemical equation tell the relativevolumes of reactants and products, expressed in any suitable unit ofvolume.

________ 9. To calculate the mass of a molecule in grams, you can use the molarmass and Avogadro’s number.

6

5

4

32

1

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Name ___________________________ Date ___________________ Class __________________©


________ 10. Because the mass of the reactants equals the mass of the products of areaction, the number of moles will be conserved.

________ 11. If the ratio of molecules in the reaction 2A2 � B2y 2A2B is 2:1:2, we canpredict that 4 molecules of A2 react with 2 molecules B2 to produce 4molecules of A2B.

________ 12. One mole of any gas occupies a volume of 22.4 L.

Part C MatchingMatch each description in Column B to the correct term in Column A.

Part D Questions and ProblemsAnswer the following in the space provided. Show your work.

18. Interpret the following equation using moles, molecules, and volumes (assumeSTP). Compare the mass of the reactants to the mass of the product.

2N2(g) � 3O2(g)y 2N2O3(g)

19. How many moles of chlorine gas will be required to react with sufficient iron toproduce 14 moles of iron(III) chloride?

2Fe(s) � 3Cl2(g) y 2FeCl3(g)

Column B

a. Avogadro’s number

b. the calculations of quantities in chemical reactions

c. STP

d. a substance formed in a chemical reaction

e. gives the relative number of molecules involved in areaction

Column A

stoichiometry

product

coefficient

6.02 � 1023

0°C, 101.3 kPa

________ 13.

________ 14.

________ 15.

________ 16.

________ 17.

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CHEMICAL CALCULATIONS12.2

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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, usingunits of moles, mass, representative particles, and volumes of gases at STP

Key Equations• mole-mole relationship used in every stoichiometric calculation:

aGuy bW(given quantity) (wanted quantity)

• x mol G � �ba

mm

oo

llWG

� � �xab� mol W

Given Mole Ratio Calculated


Mole ratios from balanced equations may be used to solve 1.

problems with other units such as numbers of and 2.

of gases at STP. The from the balanced equation are used 3.

to write conversion factors called . These conversion factors 4.

are used to calculate the numbers of moles of from a given 5.

number of moles of . In mass-mass calculations, the molar 6.

mass is used to convert mass to . 7.


________ 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 themass of SnF2 produced according to the equation:Sn(s) � 2HF(g) y SnF2(s) � H2(g)

7

6

5

4

3

21

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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, theydo not enter into the determination of significant figures.

Part C MatchingMatch each conversion problem in Column A to the correct solution in Column B.

Column A Column B

________ 15. moles O2y grams O2 a. molecules � � �1m8.0

olg

�

________ 16. liters SO2y grams SO2 at STP b. liters � �2m2.4

olL

� � �6m4.1

olg

�

________ 17. molecules He y liters He(g) at STP c. mol � �3m2.0

olg

�

________ 18. grams Sn ymolecules Sn d. molecules � � �2m2.4

olL

�

________ 19. molecules H2O y grams H2O e. grams � �1m19

olg

� �

Part D Questions and ProblemsAnswer the following questions in the space provided.

20. How many liters of carbon monoxide (at STP) are needed to react with 4.8 g ofoxygen 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 ofoxygen in the following reaction?

4NH3(g) � 7O2(g) y 6H2O(g) � 4NO2(g)

6.02 � 1023 molecules��

mol

mol��6.02 � 1023molecules

mol��6.02 � 1023 molecules

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LIMITING REAGENT AND PERCENT YIELD12.3

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Section ReviewObjectives• 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 appropriateinformation

Vocabulary

Key Equations• percent yield ��

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Whenever quantities of two or more reactants are given in a 1.

stoichiometric problem, you must identify the . This is the 2.

reagent that is completely in the reaction. The amount of 3.

limiting reagent determines the amount of that is formed. 4.

When an equation is used to calculate the amount of product 5.

that will form during a reaction, the value obtained is the . 6.

This is the 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 .


________ 7. Normally, the actual yield in a chemical reaction will be equal to orless than the theoretical yield.

________ 8. The actual yield of a chemical reaction can be calculated using moleratios.

6

5

4

3

2

1

• limiting reagent

• excess reagent

• theoretical yield

• actual yield

• percent yield

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________ 9. The amount of product can be determined from the amount of excessreagent.

________ 10. The percent yield of a product is 100 percent.

________ 11. If you had 100 steering wheels, 360 tires, and enough of every other partneeded 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 MatchingMatch each description in Column B to the correct term in Column A.

Part D Questions and ProblemsAnswer 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 theamount of unreacted excess reagent.

Column B

a. the ratio of the actual yield to the theoretical yield � 100

b. the amount of product actually formed when a reaction iscarried out in the laboratory

c. the reactant that determines the amount of product that canbe formed in a reaction

d. the reactant that is not completely used up in a chemicalreaction

e. the maximum amount of product that can be formed duringa reaction

Column A

actual yield

limiting reagent

theoretical yield

percent yield

excess reagent

________ 13.

________ 14.

________ 15.

________ 16.

________ 17.

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STOICHIOMETRY12

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Vocabulary ReviewMatch the correct vocabulary term to each numbered statement. Write the letter of thecorrect term on the line.

Column B

a. mole

b. stoichiometry

c. mass-mass calculation

d. reactants

e. excess reagent

f. theoretical yield

g. limiting reagent

h. quantity

i. actual yield

j. percent yield

Column A

the starting materials in a chemical reaction

a conversion factor derived from the coefficients of abalanced chemical equation interpreted in terms ofmoles

the maximum amount of product that could beformed in a reaction

the amount of a substance that contains 6.02 � 1023

representative particles of that substance

the substance completely used up in a chemicalreaction

the ratio of how much product is producedcompared to how much is expected, expressed as apercentage

the calculations of quantities in a chemical reaction

the actual amount of product in a chemical reaction

the substance left over after a reaction takes place

a stoichiometric computation in which the mass ofproducts is determined from the given mass ofreactants

________ 1.

________ 2.

________ 3.

________ 4.

________ 5.

________ 6.

________ 7.

________ 8.

________ 9.

________ 10.

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STOICHIOMETRY12

© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.

Chapter QuizFill in the word(s) that will make each statement true.

1. The in a balanced chemical equation also reveal the 1.mole ratios of the substances involved.

2. The number of moles of a product can be calculated from a 2.given number of moles of .

3. In mass-mass calculations, the molar mass is used to 3.convert mass to .

4. In addition to mass, the only quantity conserved in every 4.chemical reaction is .

5. According to the equation: 5.

2NO(g) � O2(g) y 2NO2(g),

22.4 L of O2 will react with L of NO at STP.

Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.

________ 6. The excess reagent determines the amount of product formed in a 12.3reaction.

________ 7. In the reaction 2CO(g) � O2(g) y 2CO2(g), using 4 moles of CO to 12.3react with 1 mole of O2 will result in the production of 4 moles of CO2.

________ 8. To calculate the percent yield of a reaction, you use the following relationship: 12.3

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________ 9. The total mass of the excess reagent and the limiting reagent is equal 12.3to the total mass of the products.

________ 10. The actual yield is equal to the theoretical yield. 12.3

5

12.2

412.2

312.2

212.1

12.11

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Documents

05 Chem GRSW Ch12.SE/TE · Chapter 12 Stoichiometry129 SECTION 12.2 CHEMICAL CALCULATIONS (pages 359–366) This section shows you how to construct mole ratios from balanced chemical