Deck 14: Chemical Kinetics

Question 1

The reaction A + 2B → products has been found to have the rate law,rate = k[A][B]².While holding the concentration of A constant,the concentration of B is increased to three times its initial value.By what factor does the rate of reaction increase?

A)3
B)6
C)9
D)27
E)30

Answer 1

9

Question 2

The reaction A + 2B → products was found to follow the rate law: rate = k[A]²[B].Predict by what factor the rate of reaction will increase when the concentration of A is doubled,the concentration of B is tripled,and the temperature remains constant.

A)5
B)6
C)12
D)18
E)None of these

Answer 2

12

Question 3

Sulfuryl chloride,SO₂Cl₂(g),decomposes at high temperature to form SO₂(g)and Cl₂(g).The rate constant at a certain temperature is 4.68 × 10^-5 s^-1.What is the order of the reaction?

A)Zero
B)First
C)Second
D)Third
E)More information is needed to determine the overall order.

Answer 3

First

Question 4

For the reaction BrO₃^- + 5Br^- + 6H⁺ → 3Br² + 3H₂O at a particular time,-Δ[BrO₃^-]/Δt = 1.5 × 10^-2 M/s.What is -Δ[Br^-]/Δt at the same instant?

A)13 M/s
B)7.5 × 10^-2 M/s
C)1.5 × 10^-2 M/s
D)3.0 × 10^-3 M/s
E)330 M/s

Question 5

Consider the general reaction 5Br-(aq)+ Br O₃-(aq)+ 6H+(aq)→ 3Br₂(aq)+ 3 H₂O(aq)
For this reaction,which is equal to Δ[Br2]/Δt?

A)-Δ[H₂O]/Δt
B)3Δ[Br O₃^-]/Δt
C)-5Δ[Br^-]/Δt
D)-0.6Δ[Br^-]/Δt
E)None of these choices is correct.

Question 6

For the reaction A + 2B → C,which expression is correct?

A)Δ[C]/Δt = Δ[A]/Δt
B)Δ[C]/Δt = 2Δ[B]/Δt
C)Δ[C]/Δt = -2Δ[B]/Δt
D)Δ[C]/Δt = -½Δ[B]/Δt
E)Δ[C]/Δt = -½Δ[A]/Δt

Question 7

What is the name given for the study of how fast reactions take place?

A)Reaction rate
B)Activation energy
C)Chemical kinetics
D)Reactivity
E)Half-life

Question 8

For the hypothetical reaction A + 3B → 2C,the rate should be expressed as

A)rate = Δ[A]/Δt.
B)rate = -Δ[C]/Δt.
C)rate = -3(Δ[B]/Δt).
D)rate = (1/2)(Δ[C]/Δt).
E)rate = (1/3)(Δ[B]/Δt).

Question 9

Consider the following reaction 8A(g)+ 5B(g)→ 8C(g)+ 6D(g)
If [C] is increasing at the rate of 4.0 mol L^-1 • s^-1,at what rate is [B] changing?

A)-0.40 mol L^-1• s^-1
B)-2.5 mol L^-1• s^-1
C)-4.0 mol L^-1• s^-1
D)-5.0 mol L^-1• s^-1
E)-6.4 mol L^-1• s^-1

Question 10

For the reaction C₆H₁₄(g)→ C₆H₆(g)+ 4H₂(g),ΔP(H₂)/Δt was found to be 2.5 × 10^-2 atm/s, where ΔP(H₂)is the change in pressure of hydrogen.Determine ΔP(C₆H₁₄)/Δt for this reaction at the same time.

A)2.5 × 10^-2 atm/s
B)-6.3 × 10^-3 atm/s
C)-2.5 × 10^-2 atm/s
D)0.10 atm/s
E)6.3 × 10^-3 atm/s

Question 11

What is the rate expression for the production of X,which is a gas,at constant volume?

A)rate = P_gVΔ[X]/RΔt
B)rate = -TΔ[X]/P_gVΔt
C)rate = -P_gV(Δ[X]/TΔt)
D)rate = (1/RT)(ΔP_X/Δt)
E)rate = (1/RΔP_X)(VT/Δt)

Question 12

The rate constant for a reaction is 4.65 L • mol^-1 • s^-1.What is the overall order of the reaction?

A)Zero
B)First
C)Second
D)Third
E)More information is needed to determine the overall order.

Question 13

Consider the reaction 2NH₃(g)→ N₂(g)+ 3 H₂ (g)
If the rate Δ[H₂]/Δt is 0.030 mol L^-1 • s^-1,what is Δ[N H₃]/Δt?

A)-0.045 mol L^-1• s^-1
B)-0.030 mol L^-1• s^-1
C)-0.020 mol L^-1• s^-1
D)-0.010 mol L^-1• s^-1
E)None of these choices is correct.

Question 14

Which equation best describes the average rate for the reaction shown? A(aq)+ B(aq)→ C(aq)+ D(aq)

A)rate = [C][D]
[A][B]
B)rate = +Δ[B]/Δt
C)rate = -Δ[C]/Δt
D)rate = -Δ[A]/Δt
E)rate = [A][B]
[C][D]

Question 15

For the following reaction,ΔP(C₆H₁₄)/Δt was found to be -6.2 × 10^-3 atm/s. C₆H₁₄(g)→ C₆H₆(g)+ 4H₂(g)
Determine ΔP(H₂)/Δt for this reaction at the same time.

A)6.2 × 10^-3 atm/s
B)1.6 × 10^-3 atm/s
C)2.5 × 10^-2 atm/s
D)-1.6 × 10^-3 atm/s
E)-2.5 × 10^-2 atm/s

Question 16

What are possible units for the reaction rate?

A)L • mol^-1 • s^-1
B)L² • mol^-2 • s^-1
C)s^-1
D)s^-2
E)mol • L^-1 • s^-1

Question 17

The reaction A + 2B → products has the rate law,rate = k[A][B]³.If the concentration of B is doubled while that of A is unchanged,by what factor will the rate of reaction increase?

A)2
B)4
C)6
D)8
E)9

Question 18

The reaction A + 2B → products was found to have the rate law,rate = k[A][B]².Predict by what factor the rate of reaction will increase when the concentration of A is doubled and the concentration of B is also doubled.

A)2
B)4
C)6
D)8
E)9

Question 19

Which is the correct unit for a first-order rate constant?

A)s^-1
B)M • s^-1
C)M • s
D)M ^-1 • s^-1
E)M ^-2 • s^-1

Question 20

For the overall chemical reaction shown below,which one of the following statements can be rightly assumed? 2 H₂S(g)+ O₂(g)→ 2S(s)+ 2H₂O(l)

A)The reaction is third-order overall.
B)The reaction is second-order overall.
C)The rate law is: rate = k[H₂S]² [O₂].
D)The rate law is: rate = k[H₂S] [O₂].
E)The rate law cannot be determined from the information given.

Question 21

When the reaction A → B + C is studied,a plot 1/[A]t vs.time gives a straight line with a positive slope.What is the order of the reaction with respect to A?

A)Zero
B)First
C)Second
D)Third
E)More information is needed to determine the order.

Question 22

What statement below best describes the graph representing the integrated first-order rate law?

A)A plot of [A]t vs.t yields a straight line with a negative slope equal to -k.
B)A plot of 1/[A]t vs.t yields a straight line with a negative slope equal to k.
C)A plot of ln[A]t vs.t yields a straight line with a positive slope equal to -k.
D)A plot of ln[A]t vs.t yields a straight line with a negative slope equal to -k.
E)A plot of 1/[A]t vs.t yields a straight line with a positive slope equal to k.

Question 23

A first-order reaction has a rate constant of 7.5 × 10^-3 s^-1.The time required for the reaction to be 60% complete is?

A)3.8 × 10^-3 s
B)6.9 × 10^-3 s
C)68 s
D)120 s
E)130 s

Question 24

It takes 42.0 min for the concentration of a reactant in a first-order reaction to drop from 0.45 M to 0.32 M at 25°C.How long will it take for the reaction to be 90% complete?

A)13.0 min
B)86.0 min
C)137 min
D)222 min
E)284 min

Question 25

A certain first-order reaction A → B is 25% complete in 42 min at 25°C.What is the half-life of the reaction?

A)21 min
B)42 min
C)84 min
D)120 min
E)101 min

Question 26

Which is the correct unit for a zeroth-order rate constant?

A)s^-1
B)M • s^-1
C)M • s
D)M^-1 • s^-1
E)M^-2 • s^-1

Question 27

A certain first-order reaction A → B is 25% complete in 42 min at 25°C.What is its rate constant?

A)6.8 × 10^-3 min^-1
B)8.3 × 10^-3 min^-1
C)3.3 × 10^-2 min^-1
D)-3.3 × 10^-2 min^-1
E)11 min^-1

Question 28

Cyclopropane is converted to propene in a first-order process.The rate constant is 5.4 × 10^-2 h^-1.If the initial concentration of cyclopropane is 0.150 M,what will its concentration be after 22.0 hours?

A)0.046 M
B)0.11 M
C)0.13 M
D)0.49 M
E)0.054 M

Question 29

When the reaction A → B + C is studied,a plot of ln[A]t vs.time gives a straight line with a negative slope.What is the order of the reaction with respect to A?

A)Zero
B)First
C)Second
D)Third
E)More information is needed to determine the order.

Question 30

A reaction has the following rate law: rate = k[A][B]²
In experiment 1,the concentrations of A and B are both 0.10 mol • L^-1; in experiment 2,the concentrations are both 0.30 mol • L^-1.If the temperature stays constant,what is the value of the ratio,rate(2)/rate(1)?

A)3.0
B)6.0
C)9.0
D)18
E)27

Question 31

What statement below best describes the graph representing the integrated second-order rate law?

A)A plot of [A]_t vs.t yields a straight line with a negative slope equal to -k.
B)A plot of 1/[A]_t vs.t yields a straight line with a negative slope equal to k.
C)A plot of ln[A]_t vs.t yields a straight line with a positive slope equal to -k.
D)A plot of ln[A]_t vs.t yields a straight line with a negative slope equal to -k.
E)A plot of 1/[A]_t vs.t yields a straight line with a positive slope equal to k.

Question 32

Which of the following is the correct unit for a second-order rate constant?

A)s^-1
B)M • s^-1
C)M • s
D)M^-1 • s^-1
E)M^-2 • s^-1

Question 33

Sucrose decomposes to fructose and glucose in acid solution.When ln [sucrose] is plotted vs.time,a straight line with slope of -0.208 h^-1 results.What is the rate law for the reaction?

A)Rate = (0.208 h^-1)[sucrose]²
B)Rate = (0.208 h^-1)[sucrose]
C)Rate = (0.0433 h)[sucrose]²
D)Rate = (0.0433 h)[sucrose]
E)Rate = (0.208 mol L^-1 • h^-1)[sucrose]⁰

Question 34

The first-order reaction SO₂Cl₂→ SO₂ + Cl₂ is 10% complete in 80.min.How long would it take for the reaction to be 95% complete?

A)1.8 min
B)104 min
C)530 min
D)2300 min
E)990 min

Question 35

At 25°C the rate constant for the first-order decomposition of a pesticide solution is 6.40 × 10^-3 min-1.If the starting concentration of pesticide is 0.0314 M,what concentration will remain after 62.0 min at 25°C?

A)1.14 × 10^-1 M
B)47.4 M
C)1.25 ×10^-2 M
D)2.11 × 10^-2 M
E)2.68 × 10^-2 M

Question 36

Nitric oxide gas (NO)reacts with chlorine gas according to the equation The following initial rates of reaction have been measured for the given reagent concentrations. Cl₂ (M)

A)rate = k[NO]
B)rate = k[NO][Cl₂]^1/2
C)rate = k[NO][Cl₂]
D)rate = k[NO]²[Cl₂]
E)rate = k[NO]²[Cl₂]²

Question 37

Ammonium cyanate (NH₄CNO)reacts to form urea (N H₂CON H₂).At 65°C the rate constant,k,is 3.60 L • mol^-1 • s^-1.What is the rate law for this reaction?

A)Rate = (3.60 L • mol^-1 • s^-1)[NH₄CNO]
B)Rate = (3.60 L • mol^-1 • s^-1)[NH₄CNO]²
C)Rate = (0.28 mol • L^-1 • s^-1)[NH₄CNO]
D)Rate = (0.28 mol • L^-1 • s^-1)[NH₄CNO]²
E)Rate = (3.60 L • mol^-1 • s^-1)[N H₂CON H₂]^-1

Question 38

Tetrafluoroethylene,C₂F₄,can be converted to octafluorocyclobutane,which can be used as a refrigerant or an aerosol propellant.A plot of 1/[C₂F₄] vs.time gives a straight line with a slope of 0.0448 L •mol^-1 • s^-1.What is the rate law for this reaction?

A)Rate = 0.0448 (L • mol^-1 • s^-1)[C₂F₄]
B)Rate = 22.3 (mol • L^-1 • s)[C₂F₄]
C)Rate = 0.0448 (L • mol^-1 • s^-1)[C₂F₄]²
D)Rate = 22.3 (mol • L^-1 • s)[C₂F₄]²
E)Rate = 0.0448 s^-1 [C₂F₄]

Question 39

What is the activation energy for a reaction if k = 1.89 × 10^-8 s^-1 at 540.K and k = 2.45 × 10^-7 s^-1 at 601 K?

A)113 kJ/mol
B)83 kJ/mol
C)410 kJ/mol
D)280 kJ/mol
E)580 kJ/mol

Question 40

What is defined as the minimum amount of energy required to initiate a chemical reaction?

A)Collision energy
B)Effective collision energy
C)Reaction energy
D)Activation energy
E)Rate energy

Question 41

The reaction 2NO₂(g)→ 2NO(g)+ O₂(g)is suspected to be second order in NO₂.Which of the following kinetic plots would be the most useful to confirm whether or not the reaction is second order?

A)A plot of [NO₂]^-1 vs.t
B)A plot of ln [NO₂] vs.t
C)A plot of [NO₂] vs.t
D)A plot of ln [NO₂]^-1 vs.t
E)A plot of [NO₂]² vs.t

Question 42

For a zeroth-order reaction,if the concentration of reactant A is plotted vs.time,which corresponds to the slope of this plot?

A)1/[A]
B)k
C)1/k
D)ln[A]
E)-k

Question 43

The rate law for the reaction 3A → C is rate = 4.36 × 10^-2 L• mol^-1 • h^-1[A]² What is the half-life for the reaction if the initial concentration of A is 0.250 M?

A)0.0109 h
B)0.0629 h
C)15.9 h
D)23.9 h
E)91.7 h

Question 44

What is the slope of a plot of ln k vs.1/T for the Arrhenius equation k = Ae^-(Ea/RT)?

A)A
B)-k
C)-E_a/R
D)k
E)E_a

Question 45

What is the half-life for a zeroth-order reaction?

A)t_1/2 = k
B)t_1/2 = 1/k[A]_o
C)t_1/2 = 0.693/k[A]_o
D)t_1/2 = [A]_o/2k
E)t_1/2 = 0.693/k

Question 46

What is the half-life for a first-order reaction?

A)t_1/2 = k
B)t_1/2 = 1/k[A]_o
C)t_1/2 = 0.693/k[A]_o
D)t_1/2 = [A]_o/2k
E)t_1/2 = 0.693/k

Question 47

Butadiene,C₄H₆ (used to make synthetic rubber and latex paints).dimerizes to C₈H₁₂ with a rate law of rate = 0.014 L/mol• s [C₄H₆]².What will be the concentration of C₄H₆ after 3.0 hours if the initial concentration is 0.025 M?

A)0.0052 M
B)0.024 M
C)43 M
D)190 M
E)0.0000 M

Question 48

The rate law for the rearrangement of CH₃NC to CH₃CN at 800 K is rate = (1300 s^-1)[CH₃NC]. What is the half-life for this reaction?

A)7.69 × 10^-4 s
B)5.3 × 10^-4 s
C)1.9 × 10^-3 s
D)520 s
E)1920 s

Question 49

What is the integrated rate law for a zeroth-order reaction?

A)rate = k[A]t
B)
C)
D)
E)

Question 50

What is the integrated rate law for a first-order reaction?

A)rate = k[A]t
B)
C)
D)
E)

Question 51

What is the integrated rate law for a second-order reaction?

A)rate = k[A]t
B)
C)
D)
E)

Question 52

The rate constant for the reaction 3A → 4B is 6.00 × 10^-3 L • mol^-1 • min^-1.How long will it take the concentration of A to drop from 0.75 M to 0.25 M?

A)2.2 × 10^-3 min
B)5.5 × 10^-3 min
C)180 min
D)440 min
E)5.0 × 10²min

Question 53

What is the half-life for a first-order reaction?

A)
B)
C)
D)
E)

Question 54

For a zeroth-order reaction,if the concentration of reactant A is plotted vs.time,which corresponds to the slope of this plot?

A)1/[A]
B)k
C)1/k
D)ln[A]
E)-k

Question 55

What is the half-life for a second-order reaction?

A)
B)
C)
D)
E)

Question 56

The rate law for the reaction 3A → 2B is rate = k[A] with a rate constant of 0.0447 h^-1.What is the half-life of the reaction?

A)0.0224 h
B)0.0645 h
C)15.5 h
D)22.4 h
E)44.7 h

Question 57

What rate constant can be determined from only the half-life of a reaction?

A)Zeroth
B)First
C)Second
D)Third
E)The rate constant cannot be determined using only a rate constant for any reaction.

Question 58

For a second-order reaction,if [A]^-1 is plotted vs.time,which corresponds to the slope of this plot?

A)1/[A]
B)k
C)1/k
D)ln[A]
E)-k

Question 59

For the reaction X + Y → Z,the reaction rate is found to depend only upon the concentration of X.A plot of 1/X versus time gives a straight line. What is the rate law for this reaction?

A)rate = k [X]
B)rate = k [X]²
C)rate = k [X][Y]
D)rate = k [X]²[Y]
E)rate = k [X]²/[Y]

Question 60

What is the half-life for a second-order reaction?

A)t_1/2 = k
B)t_1/2 = 1/k[A]_o
C)t_1/2 = 0.693/k[A]_o
D)t_1/2 = [A]o/2k
E)t_1/2 = 0.693/k

Question 61

kJ/mol. Sn²⁺ + 2Co³⁺ → Sn₄⁺ + 2Co²⁺
By what factor will the rate constant increase when the temperature is raised from 10°C to 28°C? (R = 8.314 J/mol• K)

A)1.002
B)4.6
C)5.6
D)2.8
E)696

Question 62

The radioactive isotope tritium decays with a first-order rate constant k of 0.056 yr^-1.What fraction of the tritium initially in a sample is still present 30.years later?

A)0.19
B)0.60
C)0.15
D)2.8 × 10^-38
E)0.81

Question 63

The rate law for the reaction H₂O₂ + 2H⁺ + 2I^- → I₂ + 2H₂O is rate = k[H₂O₂][I^-].The following mechanism has been suggested. H₂O₂ + I^- → HOI + OH^- (slow)
OH^- + H⁺ → H₂O (fast)
HOI + H⁺ + I^- → I₂ + H₂O (fast)
Identify all intermediates included in this mechanism.

A)H⁺and I^-
B)H⁺ and HOI
C)HOI and OH^-
D)H⁺only
E)H₂O and OH^-

Question 64

The activation energy for the following first-order reaction is 102 kJ/mol. N₂O₅(g)→ 2NO₂(g)+ (1/2)O₂(g)
The value of the rate constant (k)is 1.35 × 10^-4 s^-1 at 35°C.What is the value of k at 0°C? (R =8.314 J/mol• K)

A)8.2 × 10^-7 s^-1
B)1.9 × 10^-5 s^-1
C)4.2 × 10^-5 s^-1
D)2.2 × 10^-2 s^-1
E)1.2 × 10⁶ s^-1

Question 65

The reaction CH₃NC(g)→ CH₃CN(g)is first order with respect to methyl isocyanide,CH₃NC.If it takes 10.3 minutes for exactly one quarter of the initial amount of methyl isocyanide to react,what is the rate constant in units of min^-1?

A)-0.135 min^-1
B)0.0279 min^-1
C)0.089 min^-1
D)0.135 min^-1
E)35.8 min^-1

Question 66

Below is a plot of the reaction of A decomposing to form products. Based on the figure,which might be the order of the reaction with respect to A?

A)The reaction must only be zeroth order in A.
B)The reaction must only be first order in A.
C)The reaction must only be second order in A.
D)The reaction could be either first order in A or second order in A.
E)The reaction could be of any order in A.

Question 67

The following diagram represents the zeroth-order decomposition of A to form X according to the following balanced chemical equation: A → X.Each sphere represents 1.0 mmol of atoms,and the volume of the box is 1.0 L. What is the half-life of the reaction?

A)15 s
B)30 s
C)36 s
D)45 s
E)60 s

Question 68

The isomerization of cyclopropane follows first-order kinetics.The rate constant at 700.K is 6.20 × 10^-4 min^-1,and the half-life at 760.K is 29.0 min.What is the activation energy for this reaction? (R = 8.314 J/mol• K)

A)5.07 kJ/mol
B)27.0 kJ/mol
C)50.7 kJ/mol
D)160.kJ/mol
E)269 kJ/mol

Question 69

Carbon-14 is a radioactive isotope which decays with a half-life of 5730 years.What is the first-order rate constant for its decay?

A)5.25 × 10^-5 yr^-1
B)1.21 × 10^-4 yr^-1
C)1.75 × 10^-4 yr^-1
D)3.49 × 10^-4 yr^-1
E)3.97 × 103 yr^-1

Question 70

A rate constant obeys the Arrhenius equation,the factor A being 2.2 × 10¹³ s^-1 and the activation energy being 150.kJ mol^-1.What is the value of the rate constant at 227°C? (R = 8.314 J/mol• K)

A)2.1 × 10¹³ s^-1
B)6.7 × 10^-22 s^-1
C)1.5 × 10¹¹ s^-1
D)4.7 × 10^-3 s^-1
E)1.0 × 10²⁹ s^-1

Question 71

Consider reactions A,B,and C,which have the potential energy profiles shown.Assuming that the reactions have roughly the same frequency factors,which reaction is the slowest?

A)Reaction A
B)Reaction B
C)Reaction C
D)All of the reactions have the same rate.

Question 72

Consider the following potential energy profile for the A → B reaction.How many elementary steps are there?

A)1
B)2
C)3
D)4
E)5

Question 73

What is the molecularity of the following elementary reaction? NHCl₂(aq)+ OH^-(aq)→ NCl₂^-(aq)+ H₂O(l)

A)Unimolecular
B)Bimolecular
C)Termolecular
D)Tetramolecular
E)The reaction order is needed before the molecularity can be determined.

Question 74

Consider the following potential energy profile for the A → B reaction.How many intermediates are formed?

A)1
B)2
C)3
D)4
E)5

Question 75

A reactant R is being consumed in a first-order reaction.What fraction of the initial R is consumed in 4.0 half-lives?

A)0.94
B)0.88
C)0.75
D)0.13
E)0.063

Question 76

What is the name given to the slowest step in the mechanism of a reaction?

A)Catalytic step
B)Mechanistic step
C)Rate-determining step
D)Step 1
E)Rate step

Question 77

Consider the following potential energy profile for the A → B reaction.The overall reaction is________.

A)endothermic
B)exothermic

Question 78

The isomerization of methyl isocyanide,CH₃NC → CH₃CN,follows first-order kinetics.The half-lives were found to be 161 min at 199°C and 12.5 min at 230.°C.Calculate the activation energy for this reaction.(R = 8.314 J/mol • K)

A)6.17 × 10^-3 kJ/mol
B)31.4 kJ/mol
C)78.2 kJ/mol
D)124 kJ/mol
E)163 kJ/mol

Question 79

Consider the following potential energy profile for the A → B reaction.Assuming that the frequency factor for the reaction is 5.5×10¹⁰ s^-1,what is the rate constant of this first-order reaction at 310 K?

A)2 × 10² s^-1
B)5 × 10⁵ s^-1
C)1 × 10¹⁹ s^-1
D)2 × 10⁷ s^-1

Question 80

Enzymes are _______ .

A)large carbohydrate molecules
B)also called substrates
C)usually heterogeneous catalysts
D)insensitive to temperature
E)biological catalysts