Objectives• Describe how to express the rate of a chemical reaction
• Identify four factors that influence the rate of a chemical reaction
Vocabulary
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.
measure the speed of any change that occurs within 1.
a time interval. Collision theory states that particles when 2.
they collide, provided that they have enough . 3.
The rate at which a chemical reaction occurs is determined 4.
by an energy barrier. The activation energy is the 5.
energy that reactants must have to be converted to . The 6.
higher the activation energy barrier, the the reaction. 7.
Chemists help reactants overcome the activation barrier in a 8.
number of ways. Two effective methods are to increase the 9.
at which the reaction is done or use a . Rates of reaction 10.
can also be increased by the concentration of reactants.
Part B True-FalseClassify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 11. An increase in temperature will increase the rate of a reaction.
10
9
8
7
6
54
3
2
1
• rate
• collision theory
• activation energy
• activated complex
• transition state
• inhibitor
Name ___________________________ Date ___________________ Class __________________
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05_CTR_ch18 7/12/04 8:16 AM Page 458
Chapter 18 Reaction Rates and Equilibrium 459
Section Review
Objectives• Describe how the amounts of reactants and products change in a chemical
system at equilibrium
• Identify three stresses that can change the equilibrium position of a chemicalsystem
• Explain what the value of Keq indicates about the position of equilibrium
Vocabulary
Key Equation
• Keq � �[[CA
]]
c
a
�
�
[[DB]
]b
d
�
When aA � bB 1 cC � dD
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.
In principle, all reactions are . That is, reactants go to 1.
in the direction, and products go to in 2.
the direction. 3.
The point at which the rate of conversion of to 4.
and vice versa is equal is the position. The 5.
of a reversible reaction, Keq, is useful for determining the 6.
position of equilibrium. It is essentially a measure of the 7.
of products to reactants at equilibrium. The direction of change in 8.
the position of equilibrium may be predicted by applying 9.
principle. 10.
11.
11
10
9
87
6
5
432
1
• reversible reaction
• chemical equilibrium
• equilibrium position
• Le Châtelier’s principle
• equilibrium constant (Keq)
Name ___________________________ Date ___________________ Class __________________
Part B True-FalseClassify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 12. The concentrations of reactants and products in a system at dynamicequilibrium are always changing.
________ 13. A change in the pressure on a system can cause a shift in theequilibrium position.
________ 14. For a chemical equilibrium to be established, the chemical reactionmust be irreversible.
________ 15. The Keq for a certain reaction was 2 � 10�7. For this reaction atequilibrium, the concentration of the reactants is greater than theconcentration of the products.
Part C MatchingMatch each description in Column B to the correct term in Column A.
Part D ProblemSolve the following problem in the space provided. Show your work.
21. 2SO3(g) → 2SO2(g) � O2(g)
Calculate Keq for this reaction if the equilibrium concentrations are: [SO2] � 0.42M, [O2] � 0.21M, [SO3] � 0.072M
Column B
a. state of balance in which forward and reversereactions take place at the same rate
b. relative concentrations of reactants and products of areaction that has reached equilibrium
c. When stress is applied to a system at equilibrium, thesystem changes to relieve the stress.
d. reaction in which conversion of reactants to productsand products to reactants occur simultaneously
e. ratio of product concentrations to reactantconcentrations with each raised to a power given bythe number of moles of the substance in the balancedequation
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Chapter 18 Reaction Rates and Equilibrium 461
Section Review
Objectives• Describe the relationship between the solubility product constant and the
solubility of a compound
• Predict whether precipitation will occur when the two salt solutions are mixed
Vocabulary
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 is the equilibrium constant for the equilibrium 1.
between an ionic solid and its ions in solution. The term 2.
refers to the lowering of the solubility of a substance by the 3.
of a common ion. If the ion-product concentration of two ions in 4.
solution is greater than the Ksp of the compound formed from the
two ions, a(n) will form.4
3
2
1
• solubility product constant (Ksp)
• common ion
• common ion effect
Name ___________________________ Date ___________________ Class __________________
Part B MatchingMatch each description in Column B to the correct term in Column A.
Part C ProblemAnswer the following in the space provided.
8. Will a precipitate form when 0.00070 mol Na2CO3 is mixed with 0.0015 molBa(OH)2 in one liter of solution? Assume that these two salts both dissolvecompletely. Refer to Table 18.2 in your textbook.
Column B
a. an equilibrium constant that can be applied to thesolubility of electrolytes
b. a decrease in the solubility of a substance caused bythe addition of a common ion
c. an ion that is common to both salts in a solution
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05_CTR_ch18 7/12/04 8:16 AM Page 462
Chapter 18 Reaction Rates and Equilibrium 463
Section Review
Objectives• Identify two characteristics of spontaneous reactions
• Describe the role of entropy in chemical reactions
• Identify two factors that determine the spontaneity of a reaction
• Define Gibbs free-energy change
Vocabulary
Key Equation• �G � �H � T�S
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.
Reactions that actually occur as written are called 1.
reactions. Equations for other reactions may be written, but the 2.
reactions are . All spontaneous reactions release 3.
that becomes available to do . This energy is called . 4.
It is the natural tendency for all things to go to lower 5.
and toward disorder. In addition to the change in heat 6.
energy, is a factor that determines whether a reaction 7.
is spontaneous. 8.
Entropy is a measure of the of a system. The 9.
states that processes move in the direction of disorder. 10.
11.
11
109
8
7
6
54
32
1
• free energy
• spontaneous reaction
• nonspontaneous reactions
• entropy
• law of disorder
• Gibbs free-energy change
Name ___________________________ Date ___________________ Class __________________
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Chapter 18 Reaction Rates and Equilibrium 465
Section Review
Objectives• Describe the general relationship between the value of the specific rate constant,
k, and the speed of a chemical reaction
• Interpret the hills and valleys in a reaction progress curve
Vocabulary
Key Equation• rate � k[A]a[B]b
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 of a reaction is dependent in part on the 1.
of the reactants. An equation that relates reaction 3.
rate to reactant concentration is called a . In a rate law 4.
equation, k is known as the . 5.
The power to which a reaction concentration is raised is called 6.
the of the reaction in that reactant. A reaction whose rate 7.
is directly proportional to the concentration of one reactant is 8.
called a reaction. A reaction that is first order for each of 9.
two reactants is overall. The actual order of a reaction is 10.
determined by .
A single-step reaction is called an . A series of elementary
reactions combine to form the of a complex reaction.10
9
8
7
6
5
4
3
2
1
• rate law
• specific rate constant
• first-order reaction
• elementary reaction
• reaction mechanism
• intermediate
Name ___________________________ Date ___________________ Class __________________
Part B True-FalseClassify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 11. The rate order of a reaction can be determined from the balancedequation.
________ 12. There is at least one intermediate product in a chemical reaction.
________ 13. There is at least one activated complex in a chemical reaction.
________ 14. An elementary reaction is a one-step reaction.
Part C MatchingMatch each description in Column B to the correct term in Column A.
Part D QuestionAnswer the following question in the space provided.
21. Below is the reaction progress curve for a complex reaction. Describe thereaction represented by the curve (number of steps and the significance ofpoints A, B, C, and D).
Energy
Reaction Progress
A
B
C
D
Column B
a. a single-step reaction
b. reaction in which the rate is directly proportional tothe concentration of one reactant
c. a product of a reaction that becomes a reactant inanother step of the reaction
d. expression relating the rate of a reaction to theconcentration of the reactants
e. series of elementary reactions that take place duringa complex reaction
f. proportionality constant relating the concentrationsof reactants to the reaction rate
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Chapter 18 Reaction Rates and Equilibrium 467
Practice ProblemsIn your notebook, solve the following problems.
SECTION 18.1 RATES OF REACTION1. List three ways that reaction rates can generally be increased.
2. Ethyl acetate (C4H8O2) reacts with a solution of sodium hydroxide (NaOH) inwater to form sodium acetate (C2H3O2Na) and ethyl alcohol (C2H6O). Supposeat 25°C two moles of ethyl acetate react completely in four hours. How wouldyou express the rate of reaction?
3. How would the following actions likely change the rate of the reaction inproblem 2?
a. the temperature is lowered to 4°C.
b. the concentration of sodium hydroxide in water is increased.
4. Ethyl acetate and water are not miscible; thus, the reaction in problem 2 onlyoccurs at the interface of the two liquids. What would be the effect on thereaction rate of adding a solvent to make the reaction homogeneous?
SECTION 18.2 REVERSIBLE REACTIONS AND EQUILIBRIUM1. Write the expression for the equilibrium constant for this reaction:
2N2O5(g)1 4NO2(g) � O2(g)
2. Calculate the equilibrium constant for the reaction in problem 1 if theequilibrium concentrations are [N2O5] � 0.50 mol/L, [NO2] � 0.80 mol/L, [O2] �0.20 mol/L.
3. How would the equilibrium position for the equation in problem 1 be affectedby
a. an addition of O2 to the reaction vessel?
b. a decrease in the pressure?
4. The equilibrium constant for the reaction of nitrogen dioxide to form dinitrogentetroxide is 5.6.
2NO2 (g) 1 N2O4 (g)
In a one-liter container, the amount of N2O4, at equilibrium, is 0.66 mol. What isthe equilibrium concentration of NO2?
5. Write the equilibrium constant expression for each of the following reactions.
a. 4NO(g) � 2O2(g) 1 2N2O4 (g) c. CO(g) � 2H2(g) 1 CH3OH(g)
b. 2NO(g) � Br2(g) 1 2NOBr(g) d. SO2(g) � NO2(g) 1 SO3(g) � NO(g)
6. What effect would an increase in pressure have on the equilibrium positionof each reaction in problem 5?
Name ___________________________ Date ___________________ Class __________________
7. Which value of Keq indicates most favorably for product formation, Keq � 1 � 1012, Keq � 1.5, or Keq � 5.6 � 10�4?
8. Hydrogen sulfide gas decomposes into its elements and establishes anequilibrium at 1400 °C.
2H2S(g) 1 2H2(g) � S2(g)
A liter of this gas mixture at equilibrium contains 0.18 mol H2S, 0.014 mol H2,and 0.035 mol S2. Calculate the equilibrium constant, Keq, for this reaction.
SECTION 18.3 SOLUBILITY EQUILIBRIUM1. Write the solubility product expression for a. Ca(OH)2 and b. Ag2CO3.
2. What is the concentration of silver ions in a saturated solution of silver carbonate?The Ksp of Ag2CO3 is 8.1 � 10�12.
3. The equilibrium concentration of hydroxide ions in a saturated solution of iron(II)hydroxide is 1.2 � 10�5M at a certain temperature. Calculate the Ksp of Fe(OH)2 atthis temperature.
4. Strontium carbonate has a Ksp � 9.3 � 10�10 at 25�C. What is the concentration ofstrontium ions in a saturated solution of SrCO3?
5. What is the equilibrium concentration of silver ions at 25�C in a 1.0-L saturatedsolution of silver carbonate to which 0.20 mol of Na2CO3 has been added? The Ksp
of Ag2CO3 is 8.1 � 10�12 at 25�C.
6. Will a precipitate of PbSO4 form when 400.0 mL of 0.0050M MgSO4 is mixed with600.0 mL of 0.0020M Pb(NO3)2? The Ksp of PbSO4 � 6.3 � 10�7.
7. Will precipitation of CaCO3 occur when 500.0 mL of 4.2 � 10�3M CaCl2 is mixedwith 500.0 mL of 2.6 � 10�3M Na2CO3? The Ksp of CaCO3 is 4.5 � 10�9.
8. Which of these compounds would not decrease the solubility of Mg(OH)2 whenadded to a saturated solution of the compound?
NaOH, MgCl2, NaCl, KOH
SECTION 18.4 ENTROPY AND FREE ENERGY1. When gently warmed, the element iodine will sublime:
I2(s) → I2(g)
Is this process accompanied by an increase or decrease in entropy?
2. Does entropy increase or decrease when air is cooled and liquefied (changedfrom a gas to a liquid)?
3. Is the degree of disorder increasing or decreasing in these reactions?
a. H2(g) � Br2(l ) → 2HBr(g)
b. CuSO4 p 5H2O(s) → CuSO4(s) � 5H2O(g)
c. 2XeO3(s) → 2Xe(g) � 3O2(g)
4. Classify each of these systems as always spontaneous (A), never spontaneous(N), or depends on the relative magnitude of the heat and entropy changes (D).
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Chapter 18 Reaction Rates and Equilibrium 469
SECTION 18.5 THE PROGRESS OF CHEMICAL REACTIONS1. A first-order reaction has an initial reaction rate of 2.4 mol/(Lps). What is the
rate when one eighth the starting materials remain?
2. It has been experimentally determined that the rate law for the reactionbetween mercury(II) chloride and sodium oxalate is third-order overall andfirst-order with respect to HgCl2. Write the rate law for this reaction.
2HgCl2 � Na2C2O4 → 2NaCl � 2CO2 � Hg2Cl2
3. A combination reaction gave the following data. What is the rate law for thisreaction?
J � K → Μ
4. Iodide ion catalyzes the decomposition of hydrogen peroxide. The reaction isfirst-order in H2O2. What is the value of the rate constant, k, if the initial rate is0.00842 mol/(Lps)?
The initial concentration of H2O2 is 0.500 mol/L.
2H2O2 → 2H2O � O2
5. A proposed reaction mechanism has two intermediates. How many elementaryreactions are in this mechanism?
6. The reaction A � B → C is first-order in A and B, second-order overall.Complete the following table:
7. The condensation of acetic acid (C2H4O2) with methanol (CH4O) to form methylacetate (C3H6O2) and water is catalyzed by HCl.
C2H4O2 � CH4O 1HCl
C3H8O3 1HCl
C3H6O2 � H2O
a. How many elementary reactions are there in this condensation?
b. Write the formula for the reaction intermediate(s).
Name ___________________________ Date ___________________ Class __________________
Column B
a. activation energy
b. solubility product constant
c. chemical equilibrium
d. free energy
e. entropy
f. activated complex
g. inhibitor
h. equilibrium constant
i. spontaneous reactions
j. first-order reaction
Column A
________ 1. the disorder of a system
________ 2. a substance that interferes with theaction of a catalyst
________ 3. reactions that favor the formation ofproducts at the specified conditions
________ 4. the minimum energy collidingparticles must have in order to react
________ 5. equals the product of theconcentrations of the ions, eachraised to a power equal to thecoefficient of the ion in thedissociation equation
________ 6. the arrangement of atoms at the peakof the activation-energy barrier
________ 7. a reaction in which the rate is directlyproportional to the concentration ofone of the reactants
________ 8. energy that is available to do work
________ 9. when the forward and reversereactions are taking place at the samerate
________ 10. the ratio of product concentrations toreactant concentrations, with eachconcentration raised to a power givenby the number of moles of thatsubstance in the balanced equation
Vocabulary ReviewMatch the correct vocabulary term to each numbered statement. Write the letter of thecorrect term on the line.
05_CTR_ch18 7/12/04 8:16 AM Page 472
Chapter 18 Reaction Rates and Equilibrium 473
Chapter QuizChoose the best answer and write its letter on the line.
________ 1. At chemical equilibrium, the rates of the forward reaction and reverse 18.2reactions are:a. equal to 0. c. at a maximum.b. equal to each other. d. at a minimum.
________ 2. A catalyst works by: 18.1a. changing the pressure of the system.b. changing the temperature of the reactants.c. shifting the equilibrium position toward the products.d. lowering the activation energy barrier.
________ 3. The rate of a chemical reaction normally: 18.1a. increases as reactant concentration increases.b. is slowed down by a catalyst.c. decreases as temperature increases.d. decreases as reactant concentration increases.
________ 4. Activation energy is: 18.1a. heat released or absorbed in a reaction.b. the minimum energy colliding particles must have in order to react.c. the energy given off when reactants collide.d. generally very high for a reaction that takes place rapidly.
________ 5. Spontaneous reactions: 18.4a. are always exothermic.b. always take place at a rapid rate.c. always result in increased disorder of the system.d. naturally favor the formation of products.
________ 6. Given the reaction at equilibrium 18.3
Zn(OH)2(s) 1 Zn2�(aq) � 2OH�(aq)
what is the expression for the solubility product constant, Ksp, for this reaction?
a. Ksp [Zn2�] � [2OH�] c. Ksp �
b. Ksp � [Zn2�] � [OH�]2 d. Ksp �
Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 7. The value of Keq for a spontaneous reaction less than 1. 18.4
________ 8. The Gibbs free energy for a spontaneous process is negative. 18.4
________ 9. In a first-order reaction involving several reactants, the reaction rate is 18.5directly proportional to the concentration of each of the reactants.
A. MatchingMatch each description in Column B to the correct term in Column A. Write the letterof the correct description on the line.
B. Multiple ChoiceChoose the best answer and write its letter on the line.
________ 11. In which of the following physical states does a given substance have the highest entropy?a. solid c. liquidb. gas d. all of the above
________ 12. A reaction that requires free energy:a. must be endothermic.b. is nonspontaneous.c. must correspond to a decrease in entropy.d. is spontaneous.
Column B
a. the number of particles that react in a given time toform products
b. energy available to do work
c. favoring the formation of products
d. the minimum energy colliding particles must havein order to react
e. the forward and reverse reactions take place at thesame rate
f. a substance that interferes with the action of acatalyst
g. Reactants are converted to products in a single step.
h. the measure of disorder
i. the arrangement of atoms at the peak of theactivation energy barrier
j. If a stress is applied to a system in dynamicequilibrium, the system changes to relieve the stress.
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REACTION RATES AND EQUILIBRIUM18
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Chapter 18 Reaction Rates and Equilibrium 475
________ 13. When 0.1M HCl is added to the following system at equilibrium:
AgCl(s) 1 Ag�(aq) � Cl�(aq)
the point of equilibrium will shift to thea. right and the concentration of Ag�(aq) will decrease.b. right and the concentration of Ag�(aq) will increase.c. left and the concentration of Ag�(aq) will decrease.d. left and the concentration of Ag�(aq) will increase.
________ 14. In which of these systems is the entropy decreasing?a. air escaping from a tire c. salt dissolving in waterb. snow melting d. a gas condensing to a liquid
________ 15. All spontaneous processes:a. are exothermic. c. involve an increase in entropy.b. are endothermic d. release free energy.
________ 16. If a catalyst is used in a reaction:a. the energy of activation increases.b. the reaction rate does not change.c. the reaction rate increases.d. the equilibrium shifts.
________ 17. Which of the following affects the rate of a chemical reaction?a. the presence of a catalyst c. the concentration of reactantsb. the temperature d. all of the above
________ 18. What is the expression for Keq for this reaction?
2H2O(g) 1 2H2(g) � O2(g)
a. Keq � �[H
[
2
2]H�
2O[O
]
2]� c. Keq � �
[2H[2
2]H
�
2O[]O2]
�
b. Keq � �[H2
[]H
2
2
�
O][2
O2]� d. Keq � �
[H2
[]H
22
�
O][
2
O2]�
________ 19. In an equilibrium reaction with a Keq of 1 � 108
a. reactants are favored. c. products are favored.b. the reaction is nonspontaneous. d. the reaction is exothermic.
________ 20. What is the effect of adding more CO2 to the following equilibriumreaction?
CO2 � H2O 1 H2CO3
a. More H2CO3 is produced.b. More H2O is produced.c. The equilibrium is pushed in the direction of reactants.d. no change
________ 21. Doing which of the following generally increases the entropy of a substance?a. freezing it c. condensing itb. dissolving it in water d. all of the above
________ 22. The Keq of a reaction is 4 � 10�7. At equilibrium:a. the reactants are favored.b. the products are favored.c. the reactants and products are present in equal amounts.d. the rate of the reverse reaction is greater than the rate of the
________ 23. Two opposing reactions (A � B 1 C � D) occurring simultaneouslyat the same rate is an example of:a. reversibility. c. neither a nor bb. chemical equilibrium. d. both a and b
C. ProblemsSolve the following problems in the space provided. Show your work.
24. Calculate the value of Keq for this reaction at equilibrium.
2NOCl(g) 1 2NO(g) � Cl2(g)
An analysis of the equilibrium mixture in a 1-L flask gives the following results:NOCl, 0.30 mol; NO, 1.2 mol; Cl2, 0.60 mol.
25. Carbon monoxide and hydrogen are combined in the commercial preparationof methyl alcohol.
CO(g) � 2H2(g) 1 CH3OH(g)
At a certain set of conditions, the equilibrium mixture contains 0.020 mol/L ofCO, 0.60 mol/L of H2, and the equilibrium constant is 2.2 � 102. What is theconcentration of CH3OH in the equilibrium mixture?
26. Predict the changes in the equilibrium position for this reaction when thefollowing changes are made:
2A(g) � B(g) 1 4C(g) � heat
a. decrease the concentration of C
b. add more heat
c. increase the concentration of A
d. increase the pressure
In each case, state whether the change causes a shift that favors the formationof reactants or of products.
a. _____________________________________________________________________
b. _____________________________________________________________________
c. _____________________________________________________________________
d. _____________________________________________________________________
A. MatchingMatch each term in Column B to the correct description in Column A. Write the letterof the correct term on the line.
Column B
a. Le Châtelier’s principle
b. activated complex
c. entropy
d. collision theory
e. free energy
f. solubility productconstant
g. law of disorder
h. activation energy
i. equilibrium constant
j. chemical equilibrium
Column A
________ 1. when the forward and reverse reactions are takingplace at the same rate
________ 2. Things move in the direction of maximum disorderor randomness.
________ 3. the minimum energy colliding particles must havein order to react
________ 4. the ratio of product concentrations to reactantconcentrations, with each concentration raised to a power given by the number of moles of thatsubstance in the balanced equation
________ 5. the product of the concentrations of the ions, eachraised to a power equal to the coefficient of the ionin the dissociation equation
________ 6. the disorder of a system
________ 7. Atoms, ions, and molecules can form a chemicalbond between them when they collide, provided the particles have enough kinetic energy.
________ 8. energy that is available to do work
________ 9. the arrangement of atoms at the peak of theactivation energy barrier
________ 10. If a stress is applied to a system in a dynamicequilibrium, the system changes to relieve the stress.
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Chapter 18 Reaction Rates and Equilibrium 479
B. Multiple ChoiceChoose the best answer and write its letter on the line.
________ 11. According to collision theory, in order for a chemical reaction to occur, the reactant atoms must:a. make contact with each other.b. have a minimum level of kinetic energy.c. form an activated complex.d. all of the above
________ 12. In general, increasing temperature causes the rate of most chemical reactions to:a. increase. c. remain the same.b. decrease. d. vary unpredictably.
________ 13. Which of the following is true concerning the impact of increasing temperature on reaction rates?a. The number of collisions between reactant atoms is increased.b. The energy of each reactant atom is increased.c. The percentage of collisions with sufficient energy to cross the
activation energy barrier is increased.d. all of the above
________ 14. What would decrease the rate of most chemical reactions?a. increasing the concentration of reactant atomsb. increasing the size of the reactant particlesc. adding an appropriate catalystd. all of the above
________ 15. Catalysts alter the rate of a chemical reaction by:a. increasing the number of collisions between reactant atoms.b. increasing the kinetic energy of each reactant atom.c. lowering the activation energy barrier.d. being consumed in the reaction.
________ 16. Which of the following is true concerning a reaction that has reached chemical equilibrium?a. The forward reaction is occurring faster than the reverse reaction.b. The reverse reaction is occurring faster than the forward reaction.c. The forward reaction is occurring as fast as the reverse reaction.d. The mass of products is equal to the mass of reactants.
________ 17. Given the following system at equilibrium:
N2(g) � 3H2(g) 1 2NH3(g)
what would be the effect of removing NH3(g) as it is formed?a. The equilibrium would shift to the left.b. More N2(g) would be produced.c. More H2(g) would be produced.d. The equilibrium would shift to the right.
________ 18. Given the following system at equilibrium:
H2O(l) � heat 1 H2O(g)
how would a decrease in temperature affect the system?a. The equilibrium would shift to the right.b. More H2O(l) would be produced.c. More H2O(g) would be produced.d. The levels of reactants and products would remain the same.
________ 19. Which of the following would increase the yield of CO(g) in thefollowing equilibrium system?
C(s) � H2O(g) � heat 1 CO(g) � H2(g)
a. decreasing temperature c. adding H2(g)b. increasing pressure d. adding H2O(g)
________ 20. Spontaneous reactions:a. favor the formation of products.b. give substantial amounts of reactants at equilibrium.c. absorb free energy.d. have high reaction rates.
________ 21. Which of the following has the greatest entropy?a. ice c. water vaporb. water d. cannot be predicted
________ 22. The type of reaction most likely to be spontaneous is one in which:a. both enthalpy and entropy are decreased.b. enthalpy is decreased, while entropy is increased.c. both enthalpy and entropy are increased.d. enthalpy is increased, while entropy is decreased.
________ 23. What is the expression for Keq for the following reaction?
H2(g) � Cl2(g) 1 2HCl(g)
a. Keq � �[H
[2
2]
H�
C[lC]l2]
� c. Keq � �[H2
[]H
�
Cl[]C
2
l2]�
b. Keq � �[H
[
2
2]
H�
C[lC]l2]
� d. Keq � �[H2
[]H
�
Cl[]C2
l2]�
________ 24. If the equilibrium concentrations for the system in question 23 are asfollows, find the value of Keq.
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05_CTR_ch18 7/12/04 8:16 AM Page 480
Chapter 18 Reaction Rates and Equilibrium 481
C. ProblemsSolve the following problems in the space provided. Show your work.
25. Given the following system at equilibrium:
4HCl(g) � O2(g) 1 2H2O(g) � 2Cl2(g) � heat
determine the effect of each of the following changes on the equilibriumposition of the system (shifts right or left) and on the amount of Cl2(g) thatwould result (increases or decreases):
26. At equilibrium, the concentrations of the components of the reaction inproblem 25 are as follows:
