chapter 12 review questions

General Chemistry: Atoms First, 2e (McMurry and Fay)Chapter 12 The Rates and Mechanisms of Chemical Reactions

12.1 Multiple Choice Questions

1) Which term describes the measure of the increase in the concentration of a product per unit time?A) activation energyB) kineticsC) reaction rateD) reaction timeAnswer: CDiff: 1Topic: Section 12.1 Rates of Chemical Reactions

2) "Instantaneous rate" is defined as theA) change in concentration per unit time.B) equation showing how the rate depends on the concentration of each reactant.C) rate of reaction at a particular time.D) rate of reaction during a time interval.Answer: CDiff: 1Topic: Section 12.1 Rates of Chemical Reactions

3) Molecular hydrogen can be made from methane gas by the reaction below. How is the rate of disappearance of CH4 related to the rate of appearance of H2?

- = ?

CH4 (g) + H2O (l) → CO (g) + 3H2 (g)

A) +

B) +

C) + 3

D) none of theseAnswer: BDiff: 2Topic: Section 12.1 Rates of Chemical Reactions

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4) The burning of propane can be represented by the following equation:

(g) + 7 (g) → 3 (g) + 4 O(g) The general rate of this reaction may be expressed as:

A) +

B) -

C) -

D) +

Answer: DDiff: 2Topic: Section 12.1 Rates of Chemical Reactions

5) The burning of propane can be represented by the following equation:

(g) + 7 (g) → 3 (g) + 4 O(g) Which of the following relationships is true?

A) =

B) - 7 = + 4

C) - 3 = + 7

D) + 7 = - 4

Answer: CDiff: 2Topic: Section 12.1 Rates of Chemical Reactions


6) Methanol can be produced by the following reaction:CO(g) + 2 H2(g) → CH3OH(g).

How is the rate of disappearance of hydrogen gas related to the rate of appearance of methanol?

- = ?

A) +

B) +

C) + 2

D) none of theseAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical Reactions

7) Hydroquinone, HOC6H6OH, can be formed by the reaction with acetylene below:2 HCCH + 3 CO + H2O → HOC6H4OH + CO2

How is the rate of disappearance of acetylene, HCCH, related to the appearance of hydroquinone (Hq)?

- = ?

A) +

B) +

C) +

D) +

Answer: DDiff: 2Topic: Section 12.1 Rates of Chemical Reactions


8) The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person's bloodstream, is given below. If the rate of appearance of Cr2(SO4)3 is 1.24 mol/min at a particular moment, what is the rate of disappearance of C2H6O at that moment?

2 K2Cr2O7 + 8 H2SO4 + 3 C2H6O → 2 Cr2(SO4)3 + 2 K2SO4 + 11 H2OA) 0.413 mol/minB) 0.826 mol/minC) 1.86 mol/minD) 3.72 mol/minAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic

9) The decomposition of dinitrogen pentoxide is described by the chemical equation2 N2O5(g) → 4 NO2(g) + O2(g)

If the rate of disappearance of N2O5 is equal to 1.40 mol/min at a particular moment, what is the rate of appearance of NO2 at that moment?A) 0.700 mol/minB) 1.40 mol/minC) 2.80 mol/minD) 5.60 mol/minAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic


If the rate of appearance of NO2 is equal to 0.560 mol/min at a particular moment, what is the rate of appearance of O2 at that moment?A) 0.140 mol/minB) 0.280 mol/minC) 1.12 mol/minD) 2.24 mol/minAnswer: ADiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic



If the rate of appearance of O2 is equal to 2.40 mol/min at a particular moment, what is the rate of disappearance of N2O5 at that moment?A) 0.600 mol/minB) 1.20 mol/minC) 4.80 mol/minD) 9.60 mol/minAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic

12) Hydrogen peroxide decomposes to water and oxygen according to the reaction below:2 H2O2(aq) → 2 H2O(l) + O2(g)

In the presence of large excesses of I- ion, the following set of data is obtained. What is the average rate of disappearance of H2O2(aq) in M/s in the first 45.0 seconds of the reaction if 1.00 L of H2O2 reacts at 25°C and 1.00 atm pressure?

A) 9.09 × 10-7 M/sB) 3.63 × 10-6 M/sC) 4.33 × 10-5 M/sD) 1.64 × 10-4 M/sAnswer: BDiff: 2Topic: Section 12.1 Rates of Chemical Reactions


13) A concentration-time study of the gas phase reaction 2 A3 → 3 A2 produced the data in the table below.

Time (s) [A3] (M) [A2] (M)0 4.00 × 10–4 010 2.00 × 10–4 3.00 × 10–420 1.00 × 10–4 4.50 × 10–430 5.00 × 10–5 ?

What is the average rate of decomposition of A3 in the time interval 20-30 seconds?A) 4.00 × 10–4 M/sB) 3.50 × 10–5 M/sC) 5.00 × 10–6 M/sD) 4.00 × 10–6 M/sAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical Reactions


Time (s) [A3] (M) [A2] (M)0 4.00 × 10–4 010 2.00 × 10–4 3.00 × 10–420 1.00 × 10–4 4.50 × 10–430 5.00 × 10–5 ?

What is the average rate of formation of A2 in the time interval 20-30 seconds?A) 6.00 × 10–4 M/sB) 5.25 × 10–5 M/sC) 7.50 × 10–6 M/sD) 6.00 × 10–6 M/sAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical Reactions



Time (s) [A3] (M) [A2] (M)0 4.00 × 10–4 010 2.00 × 10–4 3.00 × 10–420 1.00 × 10–4 4.50 × 10–430 5.00 × 10–5 ?

What is the concentration of A2 after 30 seconds?A) 5.00 × 10–4 MB) 5.25 × 10–4 MC) 5.50 × 10–4 MD) 6.00 × 10–4 MAnswer: BDiff: 3Topic: Section 12.1 Rates of Chemical Reactions

16) Which statement is true for the general rate law: Rate = k[A]m[B]n?A) It can be written from the stoichiometry of the overall reaction.B) The overall order of the reaction is equal to m times n.C) The values for the exponents must be determined by experiment.D) The exponents in the rate law must be positive integers.Answer: CDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order

17) The reaction shown below has the rate law: Rate = k[BrO3–][Br–][H+]2. BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l)

What is the overall order of reaction?A) firstB) secondC) thirdD) fourthAnswer: DDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order


18) For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of A is increased by a factor of 3.00? The rate willA) decrease by a factor of 1/9.00.B) decrease by a factor of 1/3.00.C) increase by a factor of 3.00.D) increase by a factor of 9.00.Answer: CDiff: 2Topic: Section 12.2 Rate Laws and Reaction OrderAlgo. Option: algorithmic

19) For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of B is increased by a factor of 2.00? The rate willA) decrease by a factor of 1/4.00.B) decrease by a factor of 1/2.00.C) increase by a factor of 2.00.D) increase by a factor of 4.00.Answer: DDiff: 2Topic: Section 12.2 Rate Laws and Reaction OrderAlgo. Option: algorithmic

20) The reaction between chlorine and nitric oxide to form nitrosyl chloride is shown below. If the reaction rate doubles when the concentration of Cl2 is doubled and the rate quadruples when the concentration of NO is doubled, by what factor will the rate increase if both concentrations, NO and Cl2, are doubled?

Cl2(g) + 2 NO(g) → 2 NOCl(g)A) 2B) 4C) 8D) 16Answer: CDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order

21) The hydrolysis of tert-butyl chloride is given in the reaction below:(CH3)3CCl(aq) + H2O(l) → (CH3)3COH(aq) + H+(aq) + Cl-(aq)

If the rate law is: Rate = k[(CH3)3CCl], what is the order of the reaction with respect to water?A) zeroB) firstC) secondD) thirdAnswer: ADiff: 2Topic: Section 12.2 Rate Laws and Reaction Order


22) Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) → products. If the rate law is: Rate = k[E]2[F]-1, what is the order of reaction with respect to E?A) zeroB) firstC) secondD) thirdAnswer: CDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order

23) Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) → products. If the rate law is: Rate = k[E]2[F]-1, what is the overall order of reaction?A) zeroB) firstC) secondD) thirdAnswer: BDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order

24) The decomposition of ammonia to nitrogen and hydrogen on a tungsten filament at 800°C is independent of the concentration of ammonia at high pressures of ammonia. What is the order of the reaction with respect to ammonia?A) zeroB) firstC) secondD) thirdAnswer: ADiff: 2Topic: Section 12.2 Rate Laws and Reaction Order

25) Cerium(IV) ion reacts with thallium(I) ion in a one-step reaction shown below:2 Ce4+(aq) + Tl+(aq) → 2 Ce3+(aq) + Tl3+(aq).

If the rate law is: Rate = k[Ce4+]2[Tl+], what is the overall order of the reaction?A) firstB) secondC) thirdD) fourthAnswer: CDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order


26) What is the overall reaction order for the reaction that has the rate law: Rate = k[H2][NO]2?A) zero orderB) first orderC) second orderD) third orderAnswer: DDiff: 2Topic: Section 12.2 Rate Laws and Reaction OrderAlgo. Option: algorithmic

27) Iodide and hypochlorite ion react in aqueous solution according to the reaction below:I- + OCl- → OI- + Cl-

If the concentration of OH- in the solution is doubled, the rate of the reaction is halved. What is the order of the reaction with respect to OCl-?A) -2B) -1C) +1D) +2Answer: BDiff: 3Topic: Section 12.2 Rate Laws and Reaction Order

28) Chlorine reacts with chloroform according to the reaction given below:Cl2 + CHCl3 → CCl4 + HCl

When the initial concentration of Cl2 is doubled the reaction rate increases by a factor of 1.41. What is the order of the reaction with respect to Cl2?A) -1/2B) -1C) 1/2D) 2Answer: CDiff: 3Topic: Section 12.2 Rate Laws and Reaction Order

29) If the units for rate are M s-1, what are the units for the rate constant, k, if the overall order of the reaction is three?A) s-1B) M2 s-1C) M-1 s-1D) M-2 s-1Answer: DDiff: 2Topic: Section 12.2 Rate Laws and Reaction Order


30) Using the method of initial rates for the reaction A → B, if the initial concentration of A is doubled and the rate of reaction quadruples, what is the order of reaction with respect to A?A) zerothB) firstC) secondD) fourthAnswer: CDiff: 2Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates

31) The following set of data was obtained by the method of initial rates for the reaction:

2 HgCl2(aq) + C2O42-(aq) → 2 Cl-(aq) + 2 CO2(g) + Hg2Cl2(s)

What is the rate law for the reaction?

A) Rate = k[HgCl2][C2O42-]-2

B) Rate = k[HgCl2][C2O42-]-1

C) Rate = k[HgCl2]2[C2O42-]D) Rate = k[HgCl2][C2O42-]2Answer: DDiff: 3Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates



2 HgCl2(aq) + C2O42-(aq) → 2 Cl-(aq) + 2 CO2(g) + Hg2Cl2(s)

What is the value of the rate constant, k?

A) 1.4 × 10-8 1/M2∙sB) 1.3 × 10-7 1/M2∙sC) 1.4 × 10-5 1/M2∙sD) 1.3 × 10-4 1/M2∙sAnswer: DDiff: 4Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates

33) The following set of data was obtained by the method of initial rates for the reaction:(H3C)3CBr + OH- → (H3C)3COH + Br-

What is the order of reaction with respect to ion, OH-?

A) zeroB) firstC) secondD) none of theseAnswer: ADiff: 3Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates



(H3C)3CBr + OH- → (H3C)3COH + Br-

What is the value of the rate constant, k?

A) 8.8 × 10-4 s-1B) 4.4 × 10-4 s-1C) 1.8 × 10-4 s-1D) none of theseAnswer: BDiff: 3Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates


BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l).


A) Rate = k[BrO3-][Br-][H+]4

B) Rate = k[BrO3-][Br-][H+]-4

C) Rate = k[BrO3-][Br-][H+]-2

D) Rate = k[BrO3-][Br-][H+]2Answer: DDiff: 4Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates



BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l).

Calculate the initial rate when BrO3- is 0.30 M, Br- is 0.050 M, and H+ is 0.15 M.

A) 6.1 × 10-5 M/sB) 2.7 × 10-3 M/sC) 5.3 × 10-2 M/sD) 8.4 × 10-2 M/sAnswer: BDiff: 4Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates


S2O82-(aq) + 3 I-(aq) → 2 SO42-(aq) + I3-(aq)


A) Rate = k[S2O82-][I-]B) Rate = k[S2O82-][I-]5

C) Rate = k[S2O82-][I-]2

D) Rate = k[S2O82-]2[I-]Answer: ADiff: 3Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates



S2O82-(aq) + 3 I-(aq) → 2 SO42-(aq) + I3-(aq)

What is the initial rate when S2O82- is 0.15 M and I- is 0.15 M?

A) 4.10 × 10-6 M s-1B) 8.10 × 10-3 M s-1C) 1.22 × 10-2 M s-1D) 5.40 × 10-2 M s-1Answer: BDiff: 4Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates

39) The first-order decomposition of hydrogen peroxide occurs according to the equation2 H2O2(aq) → 2 H2O(l) + O2(g)

Using data from a concentration-time study of this reaction, which plot will produce a straight line?A) [H2O2] versus timeB) [H2O2]2 versus timeC) 1/[H2O2] versus timeD) ln[H2O2] versus timeAnswer: DDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate Law

40) For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction?A) 1.0 × 10-4 s-1B) 4.8 × 10-4 s-1C) 6.0 × 10-3 s-1D) 2.9 × 10-2 s-1Answer: BDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic


41) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a rate constant equal to 2.20 × 10-5 s-1 at 593 K. What percentage of the initial amount of SO2Cl2 will remain after 2.00 hours?A) 1.00%B) 14.7%C) 17.1%D) 85.4%Answer: DDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic

42) The first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), has a rate constant equal to 0.76 s-1 at 1000 K. How long will it take for the concentration of N2O to decrease to 42% of its initial concentration?A) 0.88 sB) 1.1 sC) 1.8 sD) 2.4 sAnswer: BDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic

43) The isomerization reaction, CH3NC → CH3CN, is first order and the rate constant is equal to 0.46 s-1 at 600 K. What is the concentration of CH3NC after 0.20 minutes if the initial concentration is 0.10 M?A) 4.0 x 10-4 MB) 9.1 x 10-4 MC) 4.0 x 10-2 MD) 9.1 x 10-2 MAnswer: ADiff: 4Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic


44) The following reaction is first order: C2H6 → 2 CH3. If the rate constant is equal to 5.5 × 10-4 s-1 at 1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.10 mol in the same container?A) 7.6 minB) 38 minC) 106 minD) 131 minAnswer: BDiff: 4Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic

45) The decomposition of cyclopropane, was observed at 500°C and its concentration was monitored as a function of time. The data set is given below. What is the order of the reaction with respect to cyclopropane?

A) zeroB) firstC) secondD) thirdAnswer: BDiff: 5Topic: Section 12.4 First-Order Reactions: The Integrated Rate Law

46) The half life of the reaction shown below is found not to depend on the concentration of H2O2(aq).

2 H2O2(aq) → 2 H2O(l) + O2(g)What is the order of this reaction?A) zerothB) firstC) secondD) thirdAnswer: BDiff: 2Topic: Section 12.5 First-Order Reactions: Half-Life


47) The rate constant, k, for a first-order reaction is equal to 4.2 × 10-4 s-1. What is the half-life for the reaction?A) 2.9 × 10-4 sB) 1.2 × 103 sC) 1.7 × 103 sD) 2.4 × 103 sAnswer: CDiff: 2Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic

48) Acetaldehyde decomposes at 750 K: CH3CHO → CO + CH4. The reaction is first order in acetaldehyde and the half-life of the reaction is found to be 530 seconds. What is the rate constant for the reaction at this temperature?A) 2.7 x 10-3 s-1B) 1.3 x 10-3 s-1C) 2.7 x 102 s-1D) 7.6 x 102 s-1Answer: BDiff: 2Topic: Section 12.5 First-Order Reactions: Half-Life

49) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a half-life of 8.75 hours at 593 K. How long will it take for the concentration of SO2Cl2 to fall to 12.5% of its initial value?A) 0.165 hrB) 3.22 hrC) 6.06 hrD) 26.2 hrAnswer: DDiff: 3Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic

50) For the first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), what is the concentration of N2O after 3 half-lives if 0.15 mol of N2O is initially placed into in a 1.00-L reaction vessel?A) 9.4 × 10-3 MB) 1.9 × 10-2 MC) 3.8 × 10-2 MD) 7.5 × 10-2 MAnswer: BDiff: 3Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic


51) Fluorine-18 is an isotope used in Positron Emission Tomography (PET) to scan the brain. If a researcher has 1.50 μg of 18F, how long before it decays to 1.0 ng? The half-life of 18F is 109.8 minutes.A) 5.2 × 10-2 hrB) 4.6 × 10-2 hrC) 19 hrD) 51 hrAnswer: CDiff: 3Topic: Section 12.5 First-Order Reactions: Half-Life

52) Iodine-131 is one of the many radioactive isotopes resulting from nuclear bomb explosions. How long would it take for 99% of the iodine-131 produced a nuclear explosion to disappear? The half-life of iodine-131 is 8.02 days.A) 53.3 daysB) 80.2 daysC) 40.7 daysD) 802 daysAnswer: ADiff: 3Topic: Section 12.6 First-Order Reactions: Radioactive Decay

53) Recent nuclear reactor accidents have contaminated many soils around the world. One of the isotopes deposited in soils is cesium-137. If the activity must fall by a factor of for contamination to disappear, how long will it take before uncontaminated crops may be grown in these soils? The half-life of cesium-137 is 30.2 years.A) 301 yearsB) 0.23 yearC) 33.1 yearsD) 0.03 yearAnswer: ADiff: 3Topic: Section 12.6 First-Order Reactions: Radioactive Decay

54) A plot of 1/[BrO-] vs time is linear for the reaction:3 BrO-(aq) → BrO3-(aq) + 2 Br-(aq)

What is the order of the reaction with respect to the hypobromite ion, BrO-?A) 0B) 1C) 2D) 3Answer: CDiff: 3Topic: Section 12.7 Second-Order Reactions


55) In aqueous solution, hypobromite ion, BrO-, reacts to produce bromate ion, BrO3-, and bromide ion, Br-, according to the following chemical equation.

3 BrO-(aq) → BrO3-(aq) + 2 Br-(aq)A plot of 1/[BrO-] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of BrO- is 0.80 M, how long will it take one-half of the BrO- ion to react?A) 4.5 × 10-2 sB) 7.1 sC) 12 sD) 22 sAnswer: DDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic

56) The second-order reaction, 2 Mn(CO)5 → Mn2(CO)10 has a rate constant equal to 3.0 × 109

M-1s-1 at 25°C. If the initial concentration of Mn(CO)5 is 1.0 × 10-5 M, how long will it take for 90.% of the reactant to disappear?A) 3.3 × 10-16 sB) 3.7 × 10-15 sC) 3.0 × 10-4 sD) 3.0 × 103 sAnswer: CDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic

57) Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation.

2 NO2(g) → 2 NO(g) + O2(g). A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300°C. If the half-life and the rate constant at 300°C are 11 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the original sample?A) 0.17 molB) 0.42 molC) 5.9 molD) 15 molAnswer: BDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic


58) Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation.

2 HI(g) → H2(g) + I2(g)At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 × 10-2 M to 3.50 × 10-2 M. What is the rate constant for the reaction at this temperature?A) 5.12 × 10-4 M-1s-1B) 9.69 × 10-2 M-1s-1C) 10.3 M-1s-1D) 1.95 × 103 M-1s-1Answer: BDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic

59) The reaction: 2 HI → H2 + I2, is second order and the rate constant at 800 K is 9.70 × 10-2 M-1 s-1. How long will it take for 8.00 × 10-2 mol/L of HI to decrease to one-fourth of its initial concentration?A) 0.619 sB) 124 sC) 387 sD) 429 sAnswer: CDiff: 3Topic: Section 12.7 Second-Order Reactions

60) Which statement below regarding the half-life of a second-order reaction is true?A) Each half-life is half as long as the preceding one.B) Each half-life is twice as long as the preceding one.C) Each half-life is four times as long as the preceding one.D) The length of the half-life remains unchanged throughout the course of the reaction.Answer: BDiff: 2Topic: Section 12.7 Second-Order Reactions

61) For the hypothetical second order reaction: A → products, the general rate law is: rate = k[A]2. How long is the third half-life of the reaction if [A]0 is 0.080 M and the first half-life is 22 minutes?A) 0.57 minB) 1.7 minC) 7.3 minD) 88 minAnswer: DDiff: 2Topic: Section 12.7 Second-Order Reactions


62) If the units for rate are M s-1, what are the units for the rate constant, k, for a zeroth-order reaction?A) s-1B) M-1C) M s-1D) M-1 s-1Answer: CDiff: 2Topic: Section 12.8 Zeroth-Order Reactions

63) For the zeroth-order reaction: C → products, -Δ[C]/Δt = k, which of the following graphs would be expected to give a straight line?A) [C] vs. tB) ln[C] vs. t C) 1/[C] vs. tD) [C]2 vs. tAnswer: ADiff: 2Topic: Section 12.8 Zeroth-Order Reactions

64) For the zeroth-order reaction: A → products, what will happen to the rate of reaction if the concentration of A is doubled?A) The rate will be halved.B) The rate will be doubled.C) The rate will be quadrupled.D) The rate will remain the same.Answer: DDiff: 2Topic: Section 12.8 Zeroth-Order Reactions

65) Which statement below regarding the half-life of a zeroth-order reaction is true?A) Each half-life is half as long as the preceding half-life.B) Each half-life is twice as long as the preceding half-life.C) Each half-life is four times as long as the preceding half-life.D) The half-life remains unchanged throughout the course of the reaction.Answer: ADiff: 2Topic: Section 12.8 Zeroth-Order Reactions


66) The elementary reaction representing the formation of ozone: is an example of a ________ reaction.

A) unimolecularB) bimolecularC) termolecularD) tetramolecularAnswer: CDiff: 2Topic: Section 12.11 Reaction Mechanisms

67) The elementary reaction: 2 HI → H2 + I2, is an example of a ________ reaction.A) unimolecularB) bimolecularC) termolecularD) tetramolecularAnswer: BDiff: 2Topic: Section 12.11 Reaction Mechanisms

68) A mechanism for a naturally occurring reaction that destroys ozone is:Step 1: O3(g) + HO(g) → HO2(g) + O2(g)Step 2: HO2(g) + O(g) → HO(g) + O2(g)

Which species is an intermediate?A) HOB) HO2C) OD) O3Answer: BDiff: 2Topic: Section 12.11 Reaction Mechanisms

69) The decomposition of ozone in the stratosphere can occur by the following two-step mechanism:

Step 1: Br + O3 → BrO + O2Step 2: BrO + O → Br + O2

Which species is an intermediate in this mechanism?A) BrB) BrOC) OD) O3Answer: BDiff: 2Topic: Section 12.11 Reaction Mechanisms



What is the molecularity of the overall reaction?A) unimolecularB) bimolecularC) none of these because molecularity is the difference of the exponents in the rate lawD) none of these because molecularity only refers to elementary stepsAnswer: DDiff: 2Topic: Section 12.11 Reaction Mechanisms

71) A three-step mechanism has been suggested for the formation of carbonyl chloride:Step 1: Cl2 → 2 ClStep 2: Cl + CO → COClStep 3: COCl + Cl2 → COCl2 + Cl

Which species is an intermediate in the mechanism?A) ClB) COC) COClD) COCl2Answer: CDiff: 2Topic: Section 12.11 Reaction Mechanisms

72) The slowest step in a reaction mechanism is called the ________ step.A) activationB) elementaryC) rate lawD) rate-determiningAnswer: DDiff: 2Topic: Section 12.13 Rate Laws for Overall Reactions

73) Which of the following statements are true about reaction mechanisms?I. A rate law can be written from the molecularity of the slowest elementary step.II. The final rate law can include intermediates.III. The rate of the reaction is dependent on the fastest step in the mechanism.IV. A mechanism can never be proven to be the correct pathway for a reaction.A) I, II, IIIB) II, IVC) I, IIID) I, IVAnswer: DDiff: 3Topic: Section 12.13 Rate Laws for Overall Reactions


74) Which general rate law below corresponds to an elementary bimolecular reaction?A) Rate = k[A]B) Rate = k[A][B][C]C) Rate = k[A]2[B]D) Rate = k[A][B]Answer: DDiff: 2Topic: Section 12.12 Reaction Laws for Elementary Reactions

75) What is the rate law for the elementary reaction shown below?2 HI → H2 + I2

A) Rate = k[HI]B) Rate = k[HI]2C) Rate = k[H2][I2]D) Rate = k[H2][I2]/[HI]2Answer: BDiff: 2Topic: Section 12.12 Reaction Laws for Elementary Reactions

76) A three-step mechanism has been suggested for the formation of carbonyl chloride:Step 1: Cl2→ 2 Cl (fast, equilibrium)Step 2: Cl + CO → COCl (fast, equilibrium)Step 3: COCl + Cl2 → COCl2 + Cl (slow)

What is the molecularity of the rate-determining step?A) unimolecularB) bimolecularC) termolecularD) none of theseAnswer: BDiff: 2Topic: Section 12.13 Rate Laws for Overall Reactions


77) When the concentration of A is doubled, the rate for the reaction: quadruples. When the concentration of B is doubled the rate remains the same. Which mechanism below is consistent with the experimental observations?A) Step 1: A + B D (fast equilibrium)⇌Step 2: A + D → 2 C (slow)B) Step 1: A + B → D (slow)Step 2: A + D 2 C (fast equilibrium)⇌C) Step 1: 2 A → D (slow)Step 2: B + D → E (fast)Step 3: E → 2 C (fast)D) Step 1: 2 A D (fast equilibrium)⇌Step 2: B + D → E (slow)Step 3: E → 2 C (fast)Answer: CDiff: 2Topic: Section 12.13 Rate Laws for Overall Reactions

78) A gaseous reaction occurs by a two-step mechanism, shown below.Step 1: AX +Y2 AXY⇌ 2 fastStep 2: AXY2 + AX → 2 AXY slow

Including concentration of only reactants and products, what is the rate law for this reaction?A) Rate = k[AX][Y2]B) Rate = k[AXY2]/[AX][Y2]C) Rate = k[AX]2[Y2]D) Rate = k[AXY]2/[AXY2][AX]Answer: CDiff: 2Topic: Section 12.13 Rate Laws for Overall Reactions

79) What is the minimum energy barrier that must be overcome for a chemical reaction to occur?A) activation energyB) net energyC) potential energyD) rate limiting energyAnswer: ADiff: 2Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation


80) What factor affects the rate of a chemical reaction?A) collision frequencyB) fraction of collisions with sufficient energyC) orientation of moleculesD) all of the aboveAnswer: DDiff: 3Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation

81) A gas molecule at 298 K and 1 atm pressure undergoes a collision with another gas molecule approximately every ________ seconds.A) 10-15B) 10-9C) 10-6D) 10-3Answer: BDiff: 2Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation

82) The fraction of collisions with sufficient energy to react is equal toA) AB) EaC) e-Ea/RTD) pAnswer: CDiff: 2Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation

83) What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68 kJ/mol at 25°C?A) 1.2 × 10-12B) 2.7 × 10-2C) 0.96D) 8.3 × 1011Answer: ADiff: 3Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation


84) When the temperature of a gas whose activation energy is 55 kJ/mol is increased from 300 K to 320 K, the fraction of collisions with sufficient energy to reactA) decreases by a factor of 2.B) decreases by a factor of 4.C) increases by a factor of 2.D) increases by a factor of 4.Answer: DDiff: 4Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation

85) A common rule of thumb in organic chemistry is that increasing the temperature of a reaction at room temperature by 10°C doubles the rate. Calculate Ea for a reaction that follows this rule of thumb. Assume room temperature is 25°C.A) 0.576 kJB) 12.2 kJC) 38.4 kJD) 52.9 kJAnswer: DDiff: 4Topic: Section 12.10 Using the Arrhenius Equation

86) Consider a bimolecular reaction in the gas phase. Which one of the following changes in condition will not cause an increase in the rate of the reaction?A) add a catalystB) increase the temperature at constant volumeC) increase the volume at constant temperatureD) All of the above will increase the rate of reaction.Answer: CDiff: 3Topic: Section 12.14 Catalysis

87) Which part of the Arrhenius equation contains a term which measures the number of molecules that have the correct orientation for reaction?A) activation energyB) e-Ea/RTC) frequency factorD) none of theseAnswer: CDiff: 3Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation


88) The reaction for the decomposition of dinitrogen monoxide gas to form oxygen radicals is: . If the rate constant is 3.04 × 10-2 s-1 and the frequency factor is 8.00 ×

1011 s-1, what is the activation energy for the first-order reaction at 700°C?A) 0.262 kJ/molB) 38.2 kJ/molC) 180 kJ/molD) 250 kJ/molAnswer: DDiff: 4Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation

89) The reaction for the decomposition of dinitrogen monoxide gas to form an oxygen radical is: . If the activation energy is 250 kJ/mol and the frequency factor is 8.0 ×

1011 s-1, what is the rate constant for the first-order reaction at 1000 K?A) 1.1 × 10-3 s-1B) 7.0 × 10-2 s-1C) 1.6 × 1013 s-1D) 9.1 × 1024 s-1Answer: BDiff: 4Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation

90) The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the equation:

Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+

If the activation energy is 126 kJ/mol and frequency factor is 8.62 × 1017 s-1, at what temperature is the rate constant equal to 3.63 × 10-3 s-1 for the first-order reaction?A) 0°CB) 36°CC) 50°CD) 94°CAnswer: CDiff: 4Topic: Section 12.10 Using the Arrhenius Equation



Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+

If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the frequency factor, A?A) 2.4 × 10-24 min-1B) 2.4 × 10-20 min-1C) 5.2 × 1019 min-1D) 5.2 × 1023 min-1Answer: CDiff: 4Topic: Section 12.9 Reaction Rates and Temperature: Collision Theory and the Arrhenius Equation


Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+.If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the rate constant at 50°C?A) 4.4 × 10-4 min-1B) 2.2 × 10-1 min-1C) 4.6 × 100 min-1D) 2.3 × 103 min-1Answer: BDiff: 4Topic: Section 12.10 Using the Arrhenius EquationAlgo. Option: algorithmic

93) The first-order isomerization reaction: cyclopropane → propene, has a rate constant of at 470°C and What is the activation energy, Ea, for the

reaction?A) 46 kJ/molB) 110 kJ/molC) 260 kJ/molD) 380 kJ/molAnswer: CDiff: 4Topic: Section 12.10 Using the Arrhenius Equation


94) The first-order isomerization reaction: cyclopropane → propene, has a rate constant of at 470°C and an activation energy of 264 kJ/mol. What is the temperature of the

reaction when the rate constant is equal to A) 126°CB) 411°CC) 510°CD) 540°CAnswer: DDiff: 4Topic: Section 12.10 Using the Arrhenius Equation

95) The decomposition of hydrogen peroxide is given by the following reaction:2 H2O2(aq) → 2 H2O(l) + O2(g)

In the presence of KI the reaction is thought to occur by the following mechanism:Step 1: H2O2 + I- → H2O + IO-

Step 2: IO- + H2O2 → H2O + O2 + I-

What is the role of I- in this mechanism?A) catalystB) frequency factorC) intermediateD) transition stateAnswer: ADiff: 2Topic: Section 12.14 Catalysis


Which species is a catalyst?A) HOB) HO2C) OD) O3Answer: ADiff: 2Topic: Section 12.14 Catalysis


97) The decomposition of ozone in the stratosphere can occur by the following two-step mechanism:

Br + O3 → BrO + O2BrO + O → Br + O2

Which species is a catalyst in this mechanism?A) BrB) BrOC) OD) O3Answer: ADiff: 2Topic: Section 12.14 Catalysis

98) Which of the following does not affect the rate of a bimolecular reaction?A) concentrations of reactantsB) presence of a catalystC) temperatureD) All of the above affect the rate.Answer: DDiff: 1Topic: Section 12.14 Catalysis

99) An aqueous reaction occurs by a two-step mechanism, shown below.Step 1: A2X2 + Y → A2X + XYStep 2: A2X2 + XY → A2X + X2 + Y

What is the catalyst in this reaction?A) A2XB) X2C) XYD) YAnswer: DDiff: 2Topic: Section 12.14 Catalysis


Which species is a catalyst and what type of catalysis is occurring?A) HO, homogeneousB) HO, heterogeneousC) HO2, homogeneousD) HO2, heterogeneousAnswer: ADiff: 3Topic: Section 12.15 Homogeneous and Heterogeneous Catalysts


101) The Haber process is the synthesis of ammonia gas from hydrogen and nitrogen on a hot metal surface. What is the catalyst and what type of catalysis is occurring?A) H2, homogeneousB) N2, homogeneousC) NH3, homogeneousD) metal surface, heterogeneousAnswer: DDiff: 3Topic: Section 12.15 Homogeneous and Heterogeneous Catalysts

Shown is a concentration versus time plot for a reaction involving gases A, B, and C.

102) Which equation best represents the reaction?A) 4A(g) → B(g) + 2C(g)B) 4A(g) + B(g) → 2C(g)C) 2C(g) → 4A(g) + B(g)D) 2C(g) + B(g) → 4A(g)Answer: CDiff: 2Topic: Conceptual Problems


103) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5 M/s. Over the same time interval what is the rate of reaction with respect to B, Δ[B]/Δt?A) Δ[B]/Δt = Δ[A]/Δt = 3.7 × 10-5 M/sB) Δ[B]/Δt = (1/4)(Δ[A]/Δt) = (1/4)(3.7 × 10-5 M/s) = 9.2 × 10-6 M/sC) Δ[B]/Δt = (1/2)(Δ[A]/Δt) = (1/2)(3.7 × 10-5 M/s) = 1.8 × 10-5 M/sD) Δ[B]/Δt = -(1/2)(Δ[A]/Δt) = -(1/2)(3.7 × 10-5 M/s) = -1.8 × 10-5 M/sAnswer: BDiff: 3Topic: Conceptual Problems

104) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5 M/s. Over the same time interval what is the rate of reaction with respect to C, Δ[C]/Δt?A) Δ[C]/Δt = Δ[A]/Δt = 3.7 × 10-5 M/sB) Δ[C]/Δt = (1/4)(Δ[A]/Δt) = (1/4)(3.7 × 10-5 M/s) = 9.2 × 10-6 M/sC) Δ[C]/Δt = (1/2)(Δ[A]/Δt) = (1/2)(3.7 × 10-5 M/s) = 1.8 × 10-5 M/sD) Δ[C]/Δt = -(1/2)(Δ[A]/Δt) = -(1/2)(3.7 × 10-5 M/s) = -1.8 × 10-5 M/sAnswer: DDiff: 3Topic: Conceptual Problems

105) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5 M/s. What is the rate of reaction with respect to A over the time interval 700 to 800 seconds?A) 0 M/sB) less than 3.7 × 10-5 M/sC) 3.7 × 10-5 M/sD) greater than 3.7 × 10-5 M/sAnswer: BDiff: 3Topic: Conceptual Problems

106) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5 M/s. What is the rate of reaction with respect to A over the time interval 0 to 100 seconds?A) 0 M/sB) less than 3.7 × 10-5 M/sC) 3.7 × 10-5 M/sD) greater than 3.7 × 10-5 M/sAnswer: DDiff: 3Topic: Conceptual Problems


The relative initial rates of the reaction A2 + B2 → products in vessels (a)-(d) are 1:1:4:4. Unshaded spheres represent A2 molecules, and shaded spheres represent B2 molecules present at the beginning of the reaction.

107) What is the order of reaction with respect to A2?A) 0B) 1C) 2D) 3Answer: ADiff: 3Topic: Conceptual Problems

108) What is the order of reaction with respect to B2?A) 0B) 1C) 2D) 3Answer: CDiff: 3Topic: Conceptual Problems

109) What is the overall order of reaction?A) 0B) 1C) 2D) 3Answer: CDiff: 3Topic: Conceptual Problems

110) What is the rate law for this reaction?A) Rate = k[A2]2

B) Rate = k[B2]2C) Rate = k[A2][B2]D) Rate = k[A2]2[B2]2Answer: BDiff: 3Topic: Conceptual Problems


111) The following reaction is first order in A and first order in B:A + B → Products Rate = k[A][B]

What is the initial rate of this reaction in vessel (b) relative to the initial rate of this reaction in vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres represent B molecules present at the beginning of the reaction.

A) rate in vessel (b)/rate in vessel (a) = 1:2B) rate in vessel (b)/rate in vessel (a) = 1:1C) rate in vessel (b)/rate in vessel (a) = 2:1D) rate in vessel (b)/rate in vessel (a) = 4:1Answer: ADiff: 3Topic: Conceptual Problems



A) rate in vessel (b)/rate in vessel (a) = 1:2B) rate in vessel (b)/rate in vessel (a) = 1:1C) rate in vessel (b)/rate in vessel (a) = 2:1D) rate in vessel (b)/rate in vessel (a) = 4:1Answer: CDiff: 3Topic: Conceptual Problems


113) The following reaction is second order in A and first order in B:A + B → Products Rate = k[A]2[B]


A) rate in vessel (b)/rate in vessel (a) = 1:2B) rate in vessel (b)/rate in vessel (a) = 1:1C) rate in vessel (b)/rate in vessel (a) = 2:1D) rate in vessel (b)/rate in vessel (a) = 4:1Answer: ADiff: 3Topic: Conceptual Problems


What is the rate constant k of this reaction in vessel (b) relative to the rate constant k of this reaction in vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres represent B molecules.

A) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:2B) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1C) rate constant k in vessel (b)/rate constant k in vessel (a) = 2:1D) rate constant k in vessel (b)/rate constant k in vessel (a) = 4:1Answer: BDiff: 3Topic: Conceptual Problems







A) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:2B) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1C) rate constant k in vessel b)/rate constant k in vessel (a) = 2:1D) rate constant k in vessel (b)/rate constant k in vessel (a) = 4:1Answer: BDiff: 3Topic: Conceptual Problems





120) Consider the first-order reaction A → B in which A molecules (unshaded spheres) are converted to B molecules (shaded spheres). Given the following pictures at t = 0 seconds and t = 100 seconds, which picture represents the number of A and B molecules remaining at 300 seconds?

A) picture a)B) picture b)C) picture c)D) picture d)Answer: CDiff: 3Topic: Conceptual Problems


121) Consider the first-order reaction A → B in which A molecules (unshaded spheres) are converted to B molecules (shaded spheres). Given the following pictures at t = 0 seconds and t = 100 seconds, which picture represents the number of A and B molecules remaining at 200 seconds?

A) picture a)B) picture b)C) picture c)D) picture d)Answer: CDiff: 3Topic: Conceptual Problems

122) Consider the first-order decomposition of A molecules (shaded spheres) in two vessels of equal volume. What is the half-life of decomposition in vessel (b) relative to the half-life of decomposition in vessel (a)?

A) half-life in vessel (b)/half-life in vessel (a) = 4:1B) half-life in vessel (b)/half-life in vessel (a) = 2:1C) half-life in vessel (b)/half-life in vessel (a) = 3:2D) half-life in vessel (b)/half-life in vessel (a) = 1:1Answer: DDiff: 3Topic: Conceptual Problems


123) Consider the first-order decomposition of A molecules (shaded spheres) in two vessels of equal volume. What is the half-life of decomposition in vessel (b) relative to the half-life of decomposition in vessel (a)?

A) half-life in vessel (b)/half-life in vessel (a) = 4:1B) half-life in vessel (b)/half-life in vessel (a) = 2:1C) half-life in vessel (b)/half-life in vessel (a) = 3:2D) half-life in vessel (b)/half-life in vessel (a) = 1:1Answer: DDiff: 3Topic: Conceptual Problems

124) Consider the first-order decomposition of A molecules (shaded spheres) in two vessels of equal volume. How will the rate of decomposition in vessel (a) be affected if the volume of the vessel is decreased by a factor of 2?

A) decrease by 1/2B) increase by 2C) increase by 4D) stay the sameAnswer: BDiff: 3Topic: Conceptual Problems


125) Consider the first-order decomposition of A molecules (shaded spheres) in two vessels of equal volume. How will the half-life of decomposition in vessel (a) be affected if the volume of the vessel is decreased by a factor of 2?

A) decrease by 1/2B) increase by 2C) increase by 4D) stay the sameAnswer: DDiff: 3Topic: Conceptual Problems

Consider the first-order reaction A → B in which A molecules (shaded spheres) are converted to B molecules (unshaded spheres).

126) Which drawing (a)-(d) represents the reaction mixture at t = 2 minutes?A) drawing (a)B) drawing (b)C) drawing (c)D) drawing (d)Answer: BDiff: 3Topic: Conceptual Problems


127) Which drawing (a)-(d) represents the reaction mixture at t = 3 minutes?A) drawing (a)B) drawing (b)C) drawing (c)D) drawing (d)Answer: CDiff: 3Topic: Conceptual Problems

The following pictures represent the progress of a reaction in which two A molecules combine to give a more complex molecule A2, 2A → A2.

128) What is the order of reaction with respect to A?A) 0B) 1/2C) 1D) 2Answer: DDiff: 4Topic: Conceptual Problems

129) What is the time required to achieve the molecular mixture in drawing (d)?A) 4 minB) 5 minC) 7 minD) 8 minAnswer: CDiff: 1Topic: Conceptual Problems


130) Which of the elementary reactions shown above has a molecularity of one?A) elementary reaction (a)B) elementary reaction (b)C) elementary reaction (c)D) elementary reactions (a), (b), and (c)Answer: BDiff: 1Topic: Conceptual Problems

131) Which of the elementary reactions shown above has a molecularity of two?A) elementary reaction (a)B) elementary reaction (b)C) elementary reaction (c)D) elementary reactions (a), (b), and (c)Answer: ADiff: 1Topic: Conceptual Problems

132) Which of the elementary reactions shown above has a molecularity of three?A) elementary reaction (a)B) elementary reaction (b)C) elementary reaction (c)D) elementary reactions (a), (b), and (c)Answer: CDiff: 1Topic: Conceptual Problems

Consider a reaction that occurs by the following one-step mechanism:A2 + B2 → 2 AB

The potential energy profile for this reaction is shown below.


133) What is the species present at reaction stage 1?A) an intermediateB) a productC) a reactantD) a transition stateAnswer: CDiff: 1Topic: Conceptual Problems

134) What is the species present at reaction stage 2?A) an intermediateB) a productC) a reactantD) a transition stateAnswer: DDiff: 1Topic: Conceptual Problems

135) What is the species present at reaction stage 3?A) an intermediateB) a productC) a reactantD) a transition stateAnswer: BDiff: 1Topic: Conceptual Problems


136) The activation energy for the forward reaction is given by the difference in energy between which two reaction stages?A) reaction stage 2 — reaction stage 1B) reaction stage 2 — reaction stage 3C) reaction stage 1 — reaction stage 3D) reaction stage 3 — reaction stage 1Answer: ADiff: 1Topic: Conceptual Problems

137) The energy of reaction, ΔE, is given by the difference in energy between which two reaction stages?A) reaction stage 2 — reaction stage 1B) reaction stage 2 — reaction stage 3C) reaction stage 1 — reaction stage 3D) reaction stage 3 — reaction stage 1Answer: DDiff: 1Topic: Conceptual Problems


Consider a reaction that occurs by the following mechanism:A + BC → AC + BAC + D → A + CD

The potential energy profile for this reaction is shown below.

138) Transition states occur at which reaction stages?A) reaction stages 1 and 5B) reaction stages 2, 3, and 4C) reaction stages 2 and 4D) reaction stage 3Answer: CDiff: 3Topic: Conceptual Problems

139) Intermediates occur at which reaction stages?A) reaction stages 1 and 5B) reaction stages 2, 3, and 4C) reaction stages 2 and 4D) reaction stage 3Answer: DDiff: 4Topic: Conceptual Problems


140) What is the activation energy for the formation of ozone?A) 14 kJB) 392 kJC) 406 kJD) none of theseAnswer: CDiff: 3Topic: Conceptual Problems

141) What is the activation energy for the destruction of ozone?A) 14 kJB) 392 kJC) 406 kJD) none of theseAnswer: ADiff: 4Topic: Conceptual Problems


12.2 Algorithmic Questions

1) The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person's bloodstream, is given below. If the rate of appearance of Cr2(SO4)3 is 1.64 mol/min at a particular moment, what is the rate of disappearance of C2H6O at that moment?

2 K2Cr2O7 + 8 H2SO4 + 3 C2H6O → 2 Cr2(SO4)3 + 2 K2SO4 + 11 H2OA) 0.547 mol/minB) 1.09 mol/minC) 2.46 mol/minD) 4.92 mol/minAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic


If the rate of disappearance of N2O5 is equal to 1.60 mol/min at a particular moment, what is the rate of appearance of NO2 at that moment? A) 0.800 mol/minB) 1.60 mol/minC) 3.20 mol/minD) 6.40 mol/minAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic


If the rate of appearance of NO2 is equal to 0.560 mol/min at a particular moment, what is the rate of appearance of O2 at that moment?A) 0.140 mol/minB) 0.280 mol/minC) 1.12 mol/minD) 2.24 mol/minAnswer: ADiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic



If the rate of appearance of O2 is equal to 3.00 mol/min at a particular moment, what is the rate of disappearance of N2O5 at that moment?A) 0.750 mol/minB) 1.50 mol/minC) 6.00 mol/minD) 12.0 mol/minAnswer: CDiff: 2Topic: Section 12.1 Rates of Chemical ReactionsAlgo. Option: algorithmic

5) For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of A is increased by a factor of 5.00? The rate will A) decrease by a factor of 1/25.0.B) decrease by a factor of 1/5.00.C) increase by a factor of 5.00.D) increase by a factor of 25.0.Answer: CDiff: 2Topic: Section 12.2 Rate Laws and Reaction OrderAlgo. Option: algorithmic

6) For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of B is increased by a factor of 3.00? The rate willA) decrease by a factor of 1/9.00.B) decrease by a factor of 1/3.00.C) increase by a factor of 3.00.D) increase by a factor of 9.00.Answer: DDiff: 2Topic: Section 12.2 Rate Laws and Reaction OrderAlgo. Option: algorithmic

7) What is the overall reaction order for the reaction that has the rate law: Rate = k[O2] [NO ]2? A) zero orderB) first orderC) second orderD) third orderAnswer: DDiff: 2Topic: Section 12.2 Rate Laws and Reaction OrderAlgo. Option: algorithmic


8) For a particular first-order reaction, it takes 24 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction? A) 2.0 × 10-4 s-1B) 9.6 × 10-4 s-1C) 1.2 × 10-2 s-1D) 5.8 × 10-2 s-1Answer: BDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic

9) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a rate constant equal to 2.20 × 10-5 s-1 at 593 K. What percentage of the initial amount SO2Cl2 will remain after 6.00 hours? A) 1.00%B) 37.8%C) 40.2%D) 62.2%Answer: DDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic

10) The first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), has a rate constant equal to 0.76 s-1 at 1000 K. How long will it take for the concentration of N2O to decrease to 12% of its initial concentration? A) 0.62 sB) 2.8 sC) 6.3 sD) 8.4 sAnswer: BDiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic


11) The isomerization reaction, CH3NC → CH3CN, is first order and the rate constant is equal to 0.46 s-1 at 600 K. What is the concentration of CH3NC after 0.20 minutes if the initial concentration is 0.30 M? A) 1.2 × 10-3 MB) 2.7 × 10-3 MC) 1.2 × 10-1 MD) 2.7 × 10-1 MAnswer: ADiff: 3Topic: Section 12.4 First-Order Reactions: The Integrated Rate LawAlgo. Option: algorithmic

12) The following reaction is first order, C2H6 → 2 CH3. If the rate constant is equal to 5.5 × 10-4 s-1 at 1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.20 mol in the same container? A) 4.5 minB) 17 minC) 53 minD) 65 minAnswer: BDiff: 4Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic

13) The rate constant, k, for a first-order reaction is equal to 4.2 × 10-4 s-1. What is the half-life for the reaction? A) 2.9 × 10-4 sB) 1.2 × 103 sC) 1.7 × 103 sD) 2.4 × 103 sAnswer: CDiff: 2Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic


14) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a half-life of 8.75 hours at 593 K. How long will it take for the concentration of SO2Cl2 to fall to 16.5% of its initial value? A) 0.143 hrB) 2.28 hrC) 6.99 hrD) 22.7 hrAnswer: DDiff: 3Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic

15) For the first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), what is the concentration of N2O after 3 half-lives if mol of N2O is initially placed into a 1.00-L reaction vessel? A) 1.6 × 10-2 MB) 3.1 × 10-2 MC) 6.2 × 10-2 MD) 1.2 × 10-1 MAnswer: BDiff: 3Topic: Section 12.5 First-Order Reactions: Half-LifeAlgo. Option: algorithmic

16) Carbon-14, which is present in all living tissue, radioactively decays via a first-order process. A one-gram sample of wood taken from a living tree gives a rate for carbon-14 decay of 13.6 counts per minute. If the half-life for carbon-14 is 5715 years, how old is a wood sample that gives a rate for carbon-14 decay of 11.9 counts per minute?A) 5.3 × 102 yrB) 7.6 × 102 yrC) 1.1 × 103 yrD) 9.4 × 103 yrAnswer: CDiff: 5Topic: Section 12.6 First-Order Reactions: Radioactive Decay Algo. Option: algorithmic


17) In aqueous solution, hypobromite ion, BrO-, reacts to produce bromate ion, BrO3-, and bromide ion, Br-, according to the following chemical equation.

A plot of 1/[BrO-] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of BrO- is 0.80 M, how long will it take one-half of the BrO- ion to react? A) 4.5 × 10-2 sB) 7.1 sC) 12 sD) 22 sAnswer: DDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic

18) The second-order reaction 2 Mn(CO)5 → Mn2(CO)10, has a rate constant equal to 3.0 × 109

M-1 s-1 at 25°C. If the initial concentration of Mn(CO)5 is 2.0 × 10-5 M, how long will it take for 90.% of the reactant to disappear? A) 6.7 × 10-16 sB) 7.4 × 10-15 sC) 1.5 × 10-4 sD) 6.0 × 103 sAnswer: CDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic

19) Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation.

2 NO2(g) → 2 NO(g) + O2(g). A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300°C. If the half-life and the rate constant at 300°C are 11 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the original sample? A) 0.17 molB) 0.42 molC) 5.9 molD) 15 molAnswer: BDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic


20) Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation.

2HI(g) → H2(g) + I2(g)At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 × 10-2 M to 3.50 × 10-2 M. What is the rate constant for the reaction at this temperature?A) 5.12 × 10-4 M-1s-1B) 9.69 × 10-2 M-1s-1C) 10.3 M-1s-1D) 1.95 × 103 M-1s-1Answer: BDiff: 3Topic: Section 12.7 Second-Order ReactionsAlgo. Option: algorithmic

21) The activation for the following reaction is 180 kJ/mol:(g) + (g) → (g)

If the rate constant at 202°C is 4.13 × 1 , what is the rate constant at 277°C?A) 2.10 × 1B) 1.66 × 1 C) 5.39× D) 3.99 × Answer: ADiff: 4Topic: Section 12.10 Using the Arrhenius EquationAlgo. Option: algorithmic

22) The aquation of tris(1,10-phenanthroline)iron(II) in acid solution takes place according to the equation:

Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+.If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the rate constant at 35°C? A) 4.4 × 10-3 min-1B) 2.2 × 10-2 min-1C) 4.5 × 101 min-1D) 2.3 × 102 min-1Answer: BDiff: 4Topic: Section 12.10 Using the Arrhenius EquationAlgo. Option: algorithmic


12.3 Short Answer Questions

1) For the reaction shown below, if the rate of formation of O2 is 6.0 × 10–6 M/s, the rate of decomposition of N2O5 over the same time interval is ________.

2 N2O5(g) → 4 NO2(g) + O2(g)Answer: 1.2 × 10–5 M/sDiff: 3Topic: Section 12.1 Rates of Chemical Reactions

2) The reaction shown below has the rate law: Rate = k[BrO3–][Br–][H+]2. The order of reaction with respect to H+ is ________ and the overall order is ________.

BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l)Answer: 2, 4Diff: 2Topic: Section 12.2 Rate Laws and Reaction Order

3) At 300°C decomposition of NO2(g) occurs with a rate law: Rate = – k[NO2]x. If the initial rate of decomposition is 3.2 × 10–5 M/s when [NO2]o = 8.0 × 10–3 M and the initial rate of decomposition is 8.0 × 10–6 M/s when [NO2]o = 4.0 × 10–3 M, then the order of reaction with respect to NO2, x = ________.Answer: 2Diff: 3Topic: Section 12.3 Determining a Rate Law: The Method of Initial Rates

4) The decomposition of hydrogen peroxide occurs according to the equation2 H2O2(aq) → 2 H2O(l) + O2(g)

A concentration-time study of this reaction produces a straight line when ln[H2O2] is plotted versus time. Therefore, this is a ________ order reaction.

Answer: firstDiff: 2Topic: Section 12.4 First-Order Reactions: The Integrated Rate Law

5) At 55° the decomposition of N2O5 is first order, having a rate constant, k = 1.7 × 10–3 s–1. If the initial concentration of N2O5 is 6.4 × 10–3 M, the number of half-lives that are required for the N2O5 concentration to fall to 2.0 × 10–4 M is ________, and the amount of time required is ________ minutes.Answer: 5, 34Diff: 4Topic: Section 12.5 First-Order Reactions: Half-Life


6) Carbon-14 has a half-life of 5715 years. Currently living organisms decay at a rate of 15.3 disintegrations/ min per gram of carbon. If an archeological artifact has a carbon-14 decay rate of 12.0 disintegrations/ min per gram of carbon, the approximate age of the artifact is ________ years old.Answer: 2000Diff: 3Topic: Section 12.6 First-Order Reactions: Radioactive Decay

7) At an elevated temperature the decomposition of a gaseous oxide, AO2 occurs with a rate constant, k = 0.54 M–1s–1. If the half-life of this reaction is 926 seconds when [AO2] = 2.0 × 10–3 M and 462 seconds when [AO2] = 4.0 × 10–3 M, this reaction is ________ order.Answer: secondDiff: 3Topic: Section 12.7 Second-Order Reactions

8) A gaseous compound, C, undergoes catalytic decomposition at an initial rate of 0.45 M/s when [C]o = 3.0 × 10–3 M and 0.45 M/s when [C]o = 9.0 × 10–3 M. Therefore, this is a ________ order reaction.Answer: zerothDiff: 3Topic: Section 12.8 Zeroth-Order Reactions

9) A reaction occurs by a two-step mechanism, shown below.Step 1: AX2(g) → AX(g) + X(g)Step 2: AX2(g) + X(g) → AX + X2(g)

The intermediate in this reaction is ________, and the molecularity of the second step is ________.Answer: X(g), twoDiff: 3Topic: Section 12.11 Reaction Mechanisms

10) A gaseous reaction occurs by a two-step mechanism, shown below.Step 1:AX +Y2 → AXY2Step 2:AXY2 + AX → 2 AXY

If the rate law for this reaction is Rate = k[AX]2[Y2], the intermediate is ________, and step ________ is the rate-determining step.Answer: AXY2, 2Diff: 3Topic: Section 12.11 Reaction Mechanisms


11) An aqueous reaction occurs by a two-step mechanism, shown below.Step 1: A2X2 + Y → A2X + XYStep 2: A2X2 + XY → A2X + X2 + Y

In this reaction the intermediate is ________, and the catalyst is ________.Answer: XY, YDiff: 3

Topic: Section 12.14 Catalysis


chapter 12 review questions

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