05 CTR ch17 7/12/04 8:15 AM Page 429 THE FLOW OF...

Chapter 17 Thermochemistry 429

Section Review

Objectives• Explain the relationship between energy, heat, and work

• Distinguish between exothermic and endothermic processes

• Distinguish between heat capacity and specific heat

Vocabulary

Key Equations and Relationships• 1 Calorie � 1 kilocalorie � 1000 calories

• 1 J � 0.2390 cal and 4.184 J � 1 cal

• C � �m �

q�T

� �

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 energy that flows from a warm object to a cool object 1.

is called . The energy stored within the structural units of 2.

chemical substances is called chemical . The study of heat 3.

transfer during chemical reactions and changes of state is called 4.

. One of the units used to measure heat flow is the , 5.

defined as the amount of heat needed to raise 1 g of water 1°C. 6.

The SI unit of heat and energy is the , which is equal to 7.

0.2390 cal. The of a substance is the amount of heat it 8.

takes to change the temperature of 1 g of the substance 1°C.

Substances like , with low heat capacities, take a shorter time

to heat up than substances with high heat capacities, such as .8

7

6

5

43

2

1

heat (joules or calories)��mass (g) � change in temperature (°C)

• thermochemistry

• chemical potential energy

• heat

• system

• surroundings

• law of conservation of energy

• endothermic process

• exothermic process

• heat capacity

• specific heat

Name ___________________________ Date ___________________ Class __________________

THE FLOW OF ENERGY— HEAT AND WORK

17.1

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430 Core Teaching Resources

Part B True-FalseClassify each of these statements as always true, AT; sometimes true, ST; or never true, NT.

________ 9. The joule is the SI unit of force.

________ 10. Endothermic processes absorb heat from the surroundings.

________ 11. The law of conservation of energy states that in a chemical process,energy is sometimes created and sometimes destroyed.

________ 12. A system that loses heat to its surrounding is said to be exothermic,and the value of q is negative.

________ 13. A calorie is defined as the quantity of heat needed to raise thetemperature of 1 gram of pure water 1�C.

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.

19. Distinguish among the various forms of energy: chemical potential energy,work, and heat.

20. The temperature of a piece of unknown metal with a mass of 18.0 g increasesfrom 25.0�C to 40�C when the metal absorbs 124.2 J of heat. What is the specificheat of the unknown metal? Compare your answer to the values listed in Table17.2 of your textbook. What is the identity of the unknown metal?

Column B

a. a process that absorbs heat from the surroundings

b. the amount of heat required to change the temperatureof an object by exactly 1�C

c. energy that transfers from one object to anotherbecause of a temperature difference between them

d. the part of the universe being studied

e. a process that loses heat to the surroundings

Column A

heat

exothermic process

heat capacity

system

endothermic process

________ 14.

________ 15.

________ 16.

________ 17.

________ 18.

Name ___________________________ Date ___________________ Class __________________©

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

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Section Review

Objectives• Construct equations that show the enthalpy changes for chemical and physical

processes

• Calculate enthalpy changes in chemical and physical processes

Vocabulary

Key Equation• qsys � �H � qsurr � �m � C � �T, where �T � Tf � Ti


A is a device used to measure the absorption or 1.

release of heat in chemical and physical processes. For systems at 2.

constant pressure, the heat changes that occur are the same as 3.

changes in , symbolized as . To measure the 4.

enthalpy change for a reaction in aqueous solution, it is necessary 5.

to measure the and temperatures of the system 6.

and the of the water in the system.


________ 7. When a substance dissolves in water, heat is released.

________ 8. The sign of �H is negative for an exothermic reaction.

________ 9. If 129 kJ of heat is required to decompose 2 moles of NaHCO3, then258 kJ is required to decompose 4 moles of NaHCO3.

6

54

32

1

• calorimetry

• calorimeter

• enthalpy, (H)

• thermochemical equation

• heat of reaction

• heat of combustion

Name ___________________________ Date ___________________ Class __________________

MEASURING AND EXPRESSING ENTHALPY CHANGES

17.2

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________ 10. The physical state of the reactants and products in a thermochemicalreaction are not important when calculating �H of the reaction.

________ 11. In endothermic reactions, the potential energy of the product(s) ishigher than the potential energy of the reactants.

________ 12. The equation CaO(s) � H2O(l) → Ca(OH)2(s) �H � 65.2 kJ is an example of a thermochemical equation.



18. When 2 moles of nitric oxide, NO, burn in air to produce 2 moles of nitrogendioxide, 113.04 kJ of heat is produced. Write a balanced thermochemicalequation for this reaction.

19. Calculate the amount of heat produced when 34.8 g of methane, CH4, burns inan excess of oxygen, according to the following equation.

CH4(g) � 2O2(g) → CO2(g) � 2H2O(l) �H � �890.2 kJ

Column B

a. the heat of reaction for the complete burning of 1 moleof a substance

b. a chemical equation that includes the enthalpy change(�H)

c. the accurate and precise measurement of heat changesfor chemical and physical processes

d. an insulated device containing a sealed vessel that isused to measure the heat released during a combustionreaction

e. the amount of heat that a system has at a constantpressure

Column A

enthalpy (H)

heat of combustion

thermochemical equation

calorimetry

bomb calorimeter

________ 13.

________ 14.

________ 15.

________ 16.

________ 17.

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch17 7/12/04 8:15 AM 32


Section Review

Objectives• Classify, by type, the enthalpy changes that occur during melting, freezing,

boiling, and condensing

• Calculate the enthalpy changes that occur during melting, freezing, boiling, andcondensing

• Explain what thermochemical changes can occur when a solution forms

Vocabulary


The heat absorbed by 1 mole of a substance in melting from 1.

a solid to a liquid at a constant temperature is called the . 2.

The heat lost when 1 mole of a liquid solidifies at a constant 3.

temperature is called the . The quantity of heat absorbed 4.

by a melting solid is to the quantity of heat lost when the 5.

liquid solidifies. The heat of fusion for methanol is . 6.

When liquids absorb heat at their boiling points, they become 7.

vapors. The amount of heat necessary to vaporize one mole of a

given liquid is called its . is the exact opposite of

vaporization. The amount of heat released when one mole of vapor

condenses is called its .7

65

4

3

2

1

• molar heat of fusion

• molar heat of solidification

• molar heat of vaporization

• molar heat of condensation

• molar heat of solution

Name ___________________________ Date ___________________ Class __________________

HEAT IN CHANGES OF STATE17.3

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________ 8. �Hfus � � �Hsolid

________ 9. Melting and vaporization are exothermic processes.

________ 10. In order to convert 1 mole of H2O(l) to 1 mol of H2O(g), 40.7 kJ must besupplied.

________ 11. When ice melts, the temperature of the ice increases until the entiresample becomes liquid.

________ 12. When ammonium nitrate dissolves in water, the solution gets cold.This is an example of an exothermic reaction.



18. State whether the following physical and chemical changes are endothermic orexothermic.

a. melting d. fusion

b. vaporization e. freezing

c. condensation f. combustion

19. How much heat is absorbed when 28.3 g of H2O(s) at 0�C is converted to liquidat 0�C?

20. How much heat is absorbed when 5.53 mol of NH4NO3 solid is dissolved inwater? (�Hsoln � 25.7 kJ/mol)

Column B

a. the heat absorbed by 1 mole of a substance in melting from a solid to a liquid

b. the amount of heat necessary to vaporize 1 mole of a liquid

c. � ��Hcond

d. the heat change caused by dissolution of 1 mole of substance

e. the heat lost when 1 mole of a liquid solidifies at a constant temperature

Column A

molar heat of fusion

molar heat of solidification

molar heat of vaporization

�Hvap

molar heat of solution

________ 13.

________ 14.

________ 15.

________ 16.

________ 17.

Name ___________________________ Date ___________________ Class __________________©


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Section Review

Objectives• Apply Hess’s law of heat summation to find enthalpy changes for chemical and

physical processes

• Calculate enthalpy changes using standard heats of formation

Vocabulary• Hess’s law of heat summation

• standard heat of formation

Key Equation• �H0 � �Hf

0 (products) � �Hf0 (reactants)


Hess’s law of heat summation states that for a chemical 1.

equation that can be written as the of two or more steps, 2.

the change for the final equation equals the sum of the 3.

enthalpy changes for the individual steps. Hess’s law makes it 4.

possible to measure the heat of a reaction . When a 5.

reaction is reversed, the sign of �H must be . 6.

Sometimes it is hard to measure the heat for a reaction. In 7.

such cases, the is used to calculate heats of reaction 8.

at standard conditions. The standard heat of formation of a 9.

compound is the in enthalpy that accompanies the 10.

formation of mole of a compound from its elements.

The symbol used for standard heat of formation is . The

standard heat of formation of a free element in its standard state

is . The standard heat of reaction is determined by

the �Hf0 of all the reactants from the �Hf

0 of all the products.

109

8

7

6

5

4

3

2

1

Name ___________________________ Date ___________________ Class __________________

CALCULATING HEATS OF REACTION17.4

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________ 11. The standard heat of formation for a substance is determined at 100�C.

________ 12. Hess’s law of heat summation is not related to the law of conservationof energy.

________ 13. When using Hess’s law of heat summation, intermediate reactions aresummed and terms are canceled, as in algebra, to arrive at a finalequation.

________ 14. The �Hf0 for I2(g) is zero.

________ 15. The �Hf0 for H2O(l) and H2O(s) are the same.



21. Determine the heat of reaction for the following reaction.

CuO(s) � H2(g) → Cu(s) � H2O(g)

Use the following thermochemical equations.

1) CuO(s) y Cu(s) � �12

�O2(g) �H � 155 kJ

2) H2O(g) y H2(g) � �12

�O2(g) �H � 242 kJ

22. Calculate the change in enthalpy for the following reaction using standard heatsof formation. (Refer to Table 17.4 in your textbook.)

Fe2O3(s) � 3CO(g) → 2Fe(s) � 3CO2(g)

Column B

a. symbol for the standard heat of formation

b. the change in enthalpy that accompanies theformation of 1 mole of a compound from itselements

c. in going from a particular set of reactants to aparticular set of products, the enthalpy change isthe same whether the reaction takes place in onestep or in a series of steps

d. �30.91 kJ

e. �Hf0 of Cl2(g)

Column A

standard heat of formation

Hess’s law of heat summation

�Hf0

�H0 for Br2(g) → Br2(l)

zero

________ 16.

________ 17.

________ 18.

________ 19.

________ 20.

Name ___________________________ Date ___________________ Class __________________©


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Practice ProblemsIn your notebook, solve the following problems.

SECTION 17.1 THE FLOW OF ENERGY—HEAT AND WORKUse the three-step problem-solving approach you learned in Chapter 1.

1. How many kilojoules of energy are in a donut that contains 200.0 Calories?

2. What is the specific heat of a substance that has a mass of 25.0 g and requires525.0 calories to raise its temperature by 15.0�C?

3. Suppose 100.0 g of H2O(s) absorbs 1255.0 J of heat. What is the correspondingtemperature change? The specific heat capacity of H2O(s) is 2.1 J/gp�C.

4. How many joules of heat energy are required to raise the temperature of 100.0 g of aluminum by 120.0�C? The specific heat capacity of aluminum is 0.90 J/gp�C.

SECTION 17.2 MEASURING AND EXPRESSING ENTHALPY CHANGES

1. A student mixed 75.0 mL of water containing 0.75 mol HCl at 25�C with 75.0 mLof water containing 0.75 mol of NaOH at 25�C in a foam cup calorimeter. Thetemperature of the resulting solution increased to 35�C. How much heat inkilojoules was released by this reaction?

Cwater � 4.18 J/gp�C

2. Calculate the amount of heat evolved when 15.0 g of Ca(OH)2 forms from thereaction of CaO(s) � H2O(l).

CaO(s) � H2O(l) y Ca(OH)2(s) �H � �65.2 kJ

3. Calculate the amount of heat produced when 52.4 g of methane, CH4, burns inan excess of air, according to the following equation.

CH4(g) � 2O2(g) y CO2(g) � 2H2O(l) �H � �890.2 kJ

4. Balance the following equation, then calculate the enthalpy change for thereaction given that the standard heat of combustion of NH3(g) is �226 kJ/mol.

NH3(g) � O2(g) y NO(g) � H2O(g)

SECTION 17.3 HEAT IN CHANGES OF STATE1. Calculate the amount of heat needed to melt 35.0 g of ice at 0�C. Express your

answer in kilojoules.

2. Calculate the amount of heat needed to convert 190.0 g of liquid water at 18�Cto steam at 100.0�C.

3. How much heat (kJ) is released when 2.543 mol NaOH(s) is dissolved in water?

NaOH(s)H2O(l )uuy Na�(aq) � OH�(aq) �Hsoln � �445.1 kJ/mol

Name ___________________________ Date ___________________ Class __________________

THERMOCHEMISTRY17

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4. Calculate the amount of heat needed to convert 96 g of ice at �24�C to water at 28�C. The specific heat capacity of H2O(s) is 2.1 J/gp�C.

SECTION 17.4 CALCULATING HEATS OF REACTION1. What is the standard heat of reaction for the combustion of hydrogen sulfide?

Refer to Table 17.4 in your textbook.

2H2S(g) � 3O2(g) y 2H2O(g) � 2SO2(g)

2. Calculate the enthalpy change (in kJ) for the following reaction. State whetherthe reaction is exothermic or endothermic. Refer to Table 17.4 in your textbook.

CaO(s) � CO2(g) y CaCO3(s)

3. What is the enthalpy change for the formation of hydrazine, N2H4(l), from itselements?

N2(g) � 2H2(g) y N2H4(l)

Use the following reactions and enthalpy changes:

N2H4(l) � O2(g) y N2(g) � 2H2O(l) �H � �622.2 kJ

H2(g) � �12

�O2(g) y H2O(l) �H � �285.8 kJ

Name ___________________________ Date ___________________ Class __________________©


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A student performed an experiment to determine the specific heat of an unknownmetal. The data she collected is organized in the table below. Use this information toanswer the following questions.

Hot plate

foam-cup calorimeter

100°C

22°C27°C

foam-cup calorimeter � metal

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INTERPRETING GRAPHICSUse with Section 17.2

17

Quantity Trial 1 Trial 2

1. Mass of test tube � metal 118.19 g 118.21 g

2. Mass of test tube 67.86 g 67.86 g

3. Mass of metal 50.33 g 50.35 g

4. Mass of calorimeter 7.037 g 3.818 g

5. Mass of calorimeter � water 46.137 g 43.270 g

6. Mass of water 39.100 g 39.452 g

7. Initial temperature of metal 100.0�C 100.0�C

8. Initial temperature of water 22.0�C 21.0�C

9. Final temperature of water 27.0�C 26.5�C

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1. What was the final temperature of the metal?

a. Trial 1

b. Trial 2

2. What was the �T for the metal?

a. Trial 1

b. Trial 2

3. What was the �T for the water?

a. Trial 1

b. Trial 2

4. Calculate the heat change for the water. (Specific heat capacity for water is 4.184 J/gpC.)

a. Trial 1

b. Trial 2

5. Calculate the heat change for the metal.

a. Trial 1

b. Trial 2

6. Calculate the specific heat of the metal.

a. Trial 1

b. Trial 2

7. What metal might this have been?

a. aluminum b. silver c. iron d. mercury

Name ___________________________ Date ___________________ Class __________________©


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Name ___________________________ Date ___________________ Class __________________

Column B

a. calorie

b. joule

c. exothermic

d. molar heat of solution

e. molar heat of fusion

f. calorimeter

g. enthalpy

h. energy

i. Hess’s law of heatsummation

j. endothermic reaction

Column A

the quantity of heat that raises the temperature of 1 g of pure water by 1�C

the capacity to do work or to supply heat

a device used to measure the amount of heatabsorbed or released during chemical or physicalprocesses

the heat content of a substance

the SI unit of energy

the heat absorbed by 1 mole of a substance inmelting from a solid to a liquid at a constanttemperature

If two or more thermochemical equations areadded to give a final equation, their heat changescan be added to determine the final heat change.

the heat absorbed or released by the dissolution of1 mole of substance

a chemical change in which heat is absorbed

a process that loses heat to the surroundings

________ 1.

________ 2.

________ 3.

________ 4.

________ 5.

________ 6.

________ 7.

________ 8.

________ 9.

________ 10.

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THERMOCHEMISTRY17

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

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Chapter QuizChoose the best answer and write its letter on the line.

________ 1. Thermochemistry is the study of 17.1a. reaction rates. c. combustion reactions.b. heat transfer during reactions. d. stoichiometry relationships.

________ 2. A sample of glass that has a mass of 6.0 g gives off 12 J of heat. If the 17.1temperature of the sample changes by 4.0�C during this change, what is the specific heat of the glass?a. 2.0 J/gp�C c. 0.50 J/gp�Cb. 1.1 J/gp�C d. 0.45 J/gp�C

________ 3. The accurate and precise measurement of heat flow for chemical 17.1and physical processes is called:a. calorimetry. c. thermochemistry.b. stoichiometry. d. thermometry.

________ 4. Two water solutions that have a density of 1.00 g/mL are mixed, and a 17.2reaction occurs. The temperature rises from 25.0�C to 27.0�C. Given that the heat capacity is 4.18 J/gp�C and that the total mass of the water is 75.0 g, what is the heat change for the reaction?a. 6.27 J c. 314 Jb. 125 J d. 627 J

________ 5. If 4.0 mol of a substance releases 12 kJ when it decomposes, what is 17.2�H for the process, in terms of kJ per mole of reactant?a. 3.0 kJ c. 0.33 kJb. �3.0 kJ d. �0.33 kJ

________ 6. The heat absorbed by 1 mol of a substance in melting from a solid to a 17.3liquid at constant temperature is symbolized by which of these symbols?a. �Hfus c. �Hvap

b. �Hsolid d. �Hsoln

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

7. When a chemical equation is reversed, the sign of �H . 17.3

8. The value of �Hf0 of any free element in the standard state is 17.4

set at .

9. The standard heat of reaction is equal to �Hf0 of the products 17.4

�Hf0 of the reactants.

Name ___________________________ Date ___________________ Class __________________©


THERMOCHEMISTRY17

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Chapter Test A

A. MatchingMatch the correct description to each numbered term. Write the letter of the correctdescription on the line.

B. Multiple ChoiceChoose the best answer and write its letter on the line.

________ 11. The SI unit of energy isa. heat capacity. c. joule.b. calorie. d. enthalpy.

Column B

a. the quantity of heat that raises the temperatureof 1 g of pure water 1�C

b. the change in enthalpy that accompanies theformation of 1 mole of a compound from itselements, with all substances in their standardstates at 25�C

c. energy that always flows from a warmer objectto a cooler object

d. a process that loses heat to the surroundings

e. the amount of heat required to change thetemperature of an object by exactly 1�C

f. the capacity to do work or to supply heat

g. the heat absorbed or released by a chemicalreaction

h. the amount of heat required to raise thetemperature of 1 gram of a substance 1�C

i. In any chemical or physical process, energy isneither created nor destroyed.

j. a device used to measure the amount of heatabsorbed or released during chemical or

Column A

heat capacity

law of conservation of energy

heat of reaction

energy

calorimeter

specific heat

heat

standard heat of formation

calorie

exothermic process

________ 1.

________ 2.

________ 3.

________ 4.

________ 5.

________ 6.

________ 7.

________ 8.

________ 9.

________ 10.

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________ 12. How many calories are required to raise the temperature of 75.0 g ofwater from 20�C to 50�C?a. 1.50 � 103 cal c. 3750 calb. 2250 cal d. 75.0 cal

________ 13. If 1 Calorie � 4.18 kJ, how many kJ of energy can be released by anapple containing 125 Cal?a. 0.0334 kJ c. 522 kJb. 29.9 kJ d. 5.22 � 105 kJ

________ 14. The temperature of a 6.0-g sample of glass changed from 20�C to 45�Cwhen it absorbed 550 J of heat. What is the specific heat of this glasssample?a. 3.7 J/gp�C c. 2300 J/gp�Cb. 0.27 J/gp�C d. 130 J/gp�C

________ 15. The enthalpy of a system is the same as its:a. specific heat. c. heat of combustion.b. heat of reaction. d. heat content.

________ 16. When your body is warmed by an electric blanket during the winter,this process is said to bea. endothermic. c. isothermic.b. exothermic. d. none of the above

________ 17. A student mixes two water solutions with an initial temperature of 25.0�C to form a final solution with a mass of 65.0 g at 30.0�C. What isthe heat change, in kJ, for this reaction?a. 325 kJ c. 1.36 kJb. 272 kJ d. 1.95 kJ

________ 18. Given the equation 2Mg(s) � O2(g) y 2MgO(s) � 72.3 kJ, which of thefollowing is true?a. The reaction is endothermic. c. �H � �72.3 kJb. �H � �72.3 kJ d. The reaction absorbs heat.

________ 19. Given the equation in question 18, how much heat is involved in theproduction of 5.0 mol of MgO?a. 36 kJ c. 360 kJb. 72 kJ d. 180 kJ

________ 20. Given the equation Si(s) � 2Cl2(g) y SiCl2(g) y SiCl2(l) � 687 kJ, howmuch heat is produced when 106 g of Cl2 react?a. 7.28 � 104 kJ c. 360 kJb. 513 kJ d. 180 kJ

________ 21. Which of the following statements is true?a. �Hfus � �Hsolid c. �Hfus is always negative.b. �Hfus � ��Hsolid d. �Hsolid is always positive.

________ 22. How much heat, in kJ, is required to melt 54.0 g of ice at 0�C into waterat 0�C if �Hfus for water � 6.01 kJ/mol?a. 0.111 kJ c. 18.0 kJb. 325 kJ d. 8.99 kJ

Name ___________________________ Date ___________________ Class __________________©


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________ 23. How much heat is required to convert 9.00 g of water at 100�C intosteam at 100�C, if �Hvap for water � 40.7 kJ/mol?a. 20.4 kJ c. 18.0 kJb. 366 kJ d. 81.4 kJ

________ 24. If the molar heat of solution of NH4NO3 is 25.7 kJ/mol, how much heat(in kJ) would be required to dissolve 20.0 g of NH4NO3 in water?a. 103 kJ c. 0.250 kJb. 514 kJ d. 6.43 kJ

________ 25. Calculate the enthalpy change, �H in kJ, for the reaction

H2O(s) y H2(g) � �12

�O2(g)

Use the following:

H2(g) � �12

�O2(g) y H2O(l) �H � �285.9 kJH2O(s) y H2O(l) �H � �6.0 kJ

a. �291.9 kJ c. �279.9 kb. �291.9 kJ d. �279.9 kJ

C. EssayWrite a short essay for the following.

26. Distinguish between endothermic and exothermic processes. Give at least threeexamples of each that you encounter in everyday life.

D. ProblemsSolve the following problems in the space provided. Show your work.

27. Determine the specific heat of a material if a 12-g sample absorbed 96 J as itwas heated from 20�C to 40�C.

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28. If 22.0 mL of water containing 0.030 mol of HCl is mixed with 38.0 mL of watercontaining 0.030 mol of NaOH in a calorimeter such that the initial temperatureof each solution was 27.0�C and the final temperature of the mixture is 35.0�C,how much heat (in kJ) is released in the reaction? Assume that the densities ofthe solutions are 1.00 g/mL.

29. Given the equation 3CO(g) � Fe2O3(s) y 2Fe(s) � 3CO2(g) � 24.7 kJ, how muchheat is released when 56.0 g of CO react?

30. How many grams of water at 0�C can be frozen into ice at 0�C if 55.0 kJ of heat isremoved? �Hsolid for water � �6.01 kJ/mol

31. What is the enthalpy change, �H in kJ, for the following reaction?

2Mg(s) � SiCl4(l) y Si(s) � 2MgCl2(s)

Use the following:

Si(s) � 2Cl2(g) y SiCl4(l) �H � �687 kJMg(s) � Cl2(g) yMgCl2(s) �H � �641 kJ

32. What is the standard heat of reaction (�H0) for the combustion of ethane,C2H6(g), to form carbon dioxide gas and water? Write the final balancedequation for the reaction.

Standard heats of reaction:

C2H6 � �84.68 kJO2(g) � 0.0 kJCO2(g) � �393.5 kJH2O(l) � �285.5 kJ

Name ___________________________ Date ___________________ Class __________________©


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Chapter Test B

A. MatchingMatch the correct vocabulary term to each numbered statement. Write the letter of thecorrect term on the line.

B. Multiple ChoiceChoose the best answer and write its letter on the line.

________ 11. The quantity of heat that raises the temperature of 1 gram of purewater 1�C isa. heat capacity. c. a calorie.b. joule. d. heat of combustion.

Column B

a. thermochemical equation

b. joule

c. endothermic process

d. Hess’s law of heatsummation

e. chemical potential energy

f. heat of combustion

g. calorimetry

h. thermochemistry

i. molar heat of fusion

j. enthalpy

Column A

the accurate and precise measurement of heatflow for chemical and physical processes

the heat of reaction for the complete burning of 1 mole of a substance

the study of the heat transfers that occur duringchemical reactions and physical changes of state

a process that absorbs heat from thesurroundings

the heat content of a substance

If two or more thermochemical equations areadded to give a final equation, their heat changescan be added to determine the final heat change.

the energy stored in the chemical bonds of asubstance

the heat absorbed by 1 mole of a substance inmelting from a solid to a liquid at a constanttemperature

the SI unit of energy

a chemical equation that includes the enthalpychange

________ 1.

________ 2.

________ 3.

________ 4.

________ 5.

________ 6.

________ 7.

________ 8.

________ 9.

________ 10.

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________ 12. The amount of heat required to change the temperature of an objectby exactly 1�C is the object’sa. heat of combustion. c. enthalpy.b. heat capacity. d. heat of formation.

________ 13. The number of calories required to raise the temperature of 55.0 g ofwater from 25�C to 45�C isa. 1.10 � 103 cal. c. 2480 cal.b. 1380 cal. d. 55.0 cal.

________ 14. If 1 Calorie � 4.18 kJ, how many kJ of energy can be released by abanana containing 150 Cal?a. 6.3 � 105 kJ c. 36 kJb. 0.028 kJ d. 630 kJ

________ 15. The temperature of an 8.0-g sample of metal changed from 25�C to 50�C when it absorbed 420 J of heat. What is the specific heat of thissample?a. 130 J/gp�C c. 1300 J/gp�Cb. 2.1 J/gp�C d. 0.48 J/gp�C

________ 16. As perspiration evaporates from your skin, your body is cooled. Withrespect to your body, this process is said to bea. endothermic. c. isothermic.b. exothermic. d. none of the above.

________ 17. A student mixes two water solutions beginning at 22.0�C to form afinal solution with a mass of 58.0 g at 28.5�C. What is the heat change,in kJ, for this reaction?a. 37.3 kJ c. 27.2 kJb. 242 kJ d. 1.58 kJ

________ 18. Given the equation I2(s) � 62.4 kJ y I2(g), which of the following is true?a. The reaction is exothermic.b. �H � �62.4 kJc. �H � �62.4 kJd. The reaction releases heat.

________ 19. Given the equation in question 18, how much heat is involved in theproduction of 3.5 mol I2(g)?a. 110 kJ c. 220 kJb. 62 kJ d. 3.5 kJ

________ 20. Given the equation C3H8(g) � 5O2(g) y 3CO2(g) � 4H2O(g) � 2220 kJ,how much heat is produced when 80.0 g of O2 react?a. 1110 kJ c. 2.50 kJb. 5.55 � 103 kJ d. 1.78 � 105 kJ

________ 21. Which of the following statements is true?a. �Hvap � �Hcond c. �Hvap is always negative.b. �Hvap � ��Hcond d. �Hcond is always positive.

Name ___________________________ Date ___________________ Class __________________©


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________ 22. How much heat, in kJ, is released when 108 g of water at 0�C freezes toice at 0�C if �Hsolid for water � �6.01 kJ/mol?a. 18.0 kJ c. 649 kJb. 6.00 kJ d. 36.1 kJ

________ 23. How much heat is released in the condensation of 27.0 g of steam at100�C to water at 100�C if �Hcond for water � �40.7 kJ/mol?a. 1.51 kJ c. 61.0 kJb. 1.10 3 103 kJ d. 27.1 kJ

________ 24. If the molar heat of solution of NaOH is �445.1 kJ/mol, how muchheat (in kJ) will be released if 80.00 g of NaOH are dissolved in water?a. 22.6 kJ c. 5.564 kJb. 890.2 kJ d. 35610 kJ

________ 25. Calculate the enthalpy change, �H in kJ, for the reaction

NO(g) � �12

�O2(g) y NO2(g)

Use the following:

�12

�N2(g) � �12

�O2(g) y NO(g) �H � �90.25 kJ

�12�N2(g) � O2(g) y NO2(g) �H � �33.18 kJ

a. �123.43 kJ c. 57.07 kJb. �123.43 kJ d. �57.07 kJ

C. EssayWrite a short essay for the following.

26. Explain why a burn from steam is generally more serious than a burn from very hot water.

D. ProblemsSolve the following problems in the space provided. Show your work.

27. Determine the specific heat of a material if an 18-g sample absorbed 75 J as itwas heated from 15�C to 40�C.

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28. If 27.0 mL of water containing 0.035 mol HCl is mixed with 28.0 mL of watercontaining 0.035 mol NaOH in a calorimeter such that the initial temperature of each solution was 24.0�C and the final temperature of the mixture is 33.0�C,how much heat (in kJ) is released in the reaction? Assume that the densities ofthe solutions are 1.00 g/mL.

29. Given the equation C2H4(g) � 3O2(g) y 2CO2(g) � 2H2O(l) � 1411 kJ, how muchheat is released when 8.00 g of O2 react?

30. How many grams of ice at 0�C can be melted into water at 0�C by the addition of 75.0 kJ of heat? �Hfus for water � 6.01 kJ/mol

31. What is the enthalpy change, �H in kJ, for the following reaction:

2C(s) � O2(g) y 2CO(g)

Given the following:

C(s) � O2(g) y CO2(g) �H � �393.5 kJ2CO(g) � O2(g) y 2CO2(g) �H � �565.7 kJ

32. What is the heat of reaction (�H) for the combustion of benzene, C6H6(l), to form carbon dioxide gas and water? Write the final balanced equation for the reaction.

Standard heats of formation:

C6H6 � �48.50 kJO2(g) � 0.0 kJCO2(g) � �393.5 kJH2O(l) � �285.8 kJ

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch17 7/12/04 8:15 AM Page 450

05 CTR ch17 7/12/04 8:15 AM Page 429 THE FLOW OF...

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