Deck 14: Chemical Kinetics

Question 1

The reaction A → B is first order in [A]. Consider the following data.
The concentration of A is ________ M after 40.0 s.

A)1.3 × 10^-2
B)1.2
C)0.17
D)3.5 × 10^-4
E)0.025

Answer 1

1.3 × 10^-2

Question 2

The data in the table below were obtained for the reaction:
A + B → P
The rate law for this reaction is rate = ________.

A)k[A][B]
B)k[P]
C)k[A]²[B]
D)k[A]²[B]²
E)k[A]²

Answer 2

k[A]²

Question 3

Which one of the following is not a valid expression for the rate of the reaction below? 4NH₃ + 7O₂ → 4NO₂ + 6H₂O

A)-
B)
C)
D)-
E)All of the above are valid expressions of the reaction rate.

Answer 3

All of the above are valid expressions of the reaction rate.

Question 4

A burning splint will burn more vigorously in pure oxygen than in air because ________.

A)oxygen is a reactant in combustion and concentration of oxygen is higher in pure oxygen than is in air
B)oxygen is a catalyst for combustion
C)oxygen is a product of combustion
D)nitrogen is a product of combustion and the system reaches equilibrium at a lower temperature
E)nitrogen is a reactant in combustion and its low concentration in pure oxygen catalyzes the combustion

Question 5

The reaction A (aq) → B (aq)is first order in [A]. A solution is prepared with [A] = 1.22 M. The following data are obtained as the reaction proceeds: The rate constant for this reaction is ________ s^-1.

A)0.23
B)1.0
C)0.17
D)0.12
E)-0.12

Question 6

The data in the table below were obtained for the reaction:
2 ClO₂ (aq) + 2 OH^- (aq) → ClO₃^- (aq) + ClO₂^- (aq) + H₂O (1)
What is the order of the reaction with respect to OH^-?

A)0
B)1
C)2
D)3
E)4

Question 7

The reaction A → B is first order in [A]. Consider the following data.
The rate constant for this reaction is ________ s^-1.

A)6.9 × 10^-2
B)3.0 × 10^-2
C)14
D)0.46
E)4.0 × 10²

Question 8

The reaction A → B is first order in [A]. Consider the following data.
The rate constant of a first-order process that has a half-life of 3.50 min is ________ s^-1.

A)0.693
B)1.65 × 10^-2
C)1.98
D)0.198
E)3.30 ×10^-3

Question 9

The rate law of a reaction is rate = k[D][X]. The units of the rate constant are ________.

A)mol L^-1s^-1
B)L mol^-1s^-1
C)mol² L^-2s^-1
D)mol L^-1s^-2
E)L² mol^-2s^-1

Question 10

The reaction 2NO₂ → 2NO + O₂
Follows second-order kinetics. At 300 °C, [NO₂] drops from 0.0100 M to 0.00650 M in 100.0 s. The rate constant for the reaction is ________ M^-1s^-1.

A)0.096
B)0.65
C)0.81
D)1.2
E)0.54

Question 11

One difference between first- and second-order reactions is that ________.

A)the half-life of a first-order reaction does not depend on [A]₀; the half-life of a second-order reaction does depend on [A]₀
B)the rate of both first-order and second-order reactions do not depend on reactant concentrations
C)the rate of a first-order reaction depends on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations
D)a first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed
E)None of the above are true.

Question 12

The reaction CH₃-N≡C → CH₃-C≡N
Is a first-order reaction. At 230.3 °C, k = 6.29 × 10^-4s^-1. If is 1.00 × 10^-3 initially, is ________ after 1.000 × 10³ s.

A)5.33 × 10^-4
B)2.34 × 10^-4
C)1.88 × 10^-3
D)4.27 × 10^-3
E)1.00 × 10^-6

Question 13

Which one of the following graphs shows the correct relationship between concentration and time for a reaction that is second order in [A]?

A)
B)
C)
D)
E)

Question 14

Of the following, all are valid units for a reaction rate except ________.

A)mol/L
B)M/s
C)mol/hr
D)g/s
E)mol/L-hr

Question 15

The following reaction is second order in [A] and the rate constant is 0.025 M^-1s^-1: A → B
The concentration of A was 0.65 M at 33 s. The initial concentration of A was ________ M.

A)2.4
B)0.27
C)0.24
D)1.4
E)1.2 × 10^-2

Question 16

The data in the table below were obtained for the reaction:
2 ClO₂ (aq) + 2 OH^- (aq) → ClO₃^- (aq) + ClO₂^- (aq) + H₂O (1)
What is the order of the reaction with respect to ClO₂?

A)1
B)0
C)2
D)3
E)4

Question 17

The data in the table below were obtained for the reaction:
2 ClO₂ (aq) + 2 OH^- (aq) → ClO₃^- (aq) + ClO₂^- (aq) + H₂O (1)
What is the overall order of the reaction?

A)4
B)0
C)1
D)2
E)3

Question 18

The data in the table below were obtained for the reaction:
A + B → P
The magnitude of the rate constant is ________.

A)38.0
B)0.278
C)13.2
D)42.0
E)2.21

Question 19

The data in the table below were obtained for the reaction:
2 ClO₂ (aq) + 2 OH^- (aq) → ClO₃^- (aq) + ClO₂^- (aq) + H₂O (1)
What is the magnitude of the rate constant for the reaction?

A)1.15 × 10⁴
B)4.6
C)230
D)115
E)713

Question 20

Under constant conditions, the half-life of a first-order reaction ________.

A)is the time necessary for the reactant concentration to drop to half its original value
B)is constant
C)can be calculated from the reaction rate constant
D)does not depend on the initial reactant concentration
E)All of the above are correct.

Question 21

A catalyst can increase the rate of a reaction ________.

A)by changing the value of the frequency factor (A)
B)by increasing the overall activation energy (E_a)of the reaction
C)by lowering the activation energy of the reverse reaction
D)by providing an alternative pathway with a lower activation energy
E)All of these are ways that a catalyst might act to increase the rate of reaction.

Question 22

Which of the following is true?

A)If we know that a reaction is an elementary reaction, then we know its rate law.
B)The rate-determining step of a reaction is the rate of the fastest elementary step of its mechanism.
C)Since intermediate compounds can be formed, the chemical equations for the elementary reactions in a multistep mechanism do not always have to add to give the chemical equation of the overall process.
D)In a reaction mechanism, an intermediate is identical to an activated complex.
E)All of the above statements are true.

Question 23

For the elementary reaction NO₃ + CO → NO₂ + CO₂
The molecularity of the reaction is ________, and the rate law is

A)2, k[NO₃][CO]
B)4, k[NO₃][CO][NO₂][CO₂]
C)2, k[NO₂][CO₂]
D)2, k[NO₃][CO]/[NO₂][CO₂]
E)4, k[NO₂][CO₂]/[NO₃][CO]

Question 24

________ are used in automotive catalytic converters.

A)Heterogeneous catalysts
B)Homogeneous catalysts
C)Enzymes
D)Noble gases
E)Nonmetal oxides

Question 25

As the temperature of a reaction is increased, the rate of the reaction increases because the ________.

A)reactant molecules collide less frequently
B)reactant molecules collide more frequently and with greater energy per collision
C)activation energy is lowered
D)reactant molecules collide less frequently and with greater energy per collision
E)reactant molecules collide more frequently with less energy per collision

Question 26

The decomposition of N₂O₅ in solution in carbon tetrachloride proceeds via the reaction 2N₂O₅ (soln) → 4NO₂ (soln) + O₂ (soln)
The reaction is first order and has a rate constant of 4.82 × 10^-3 s^-1 at 64 °C. The rate law for the reaction is rate = ________.

A)k[N₂O₅]²
B)k
C)k[N₂O₅]
D)k
E)2k[N₂O₅]

Question 27

Which energy difference in the energy profile below corresponds to the activation energy for the forward reaction?

A)x
B)y
C)x + y
D)x - y
E)y - x

Question 28

In the Arrhenius equation, k = Ae^-Ea/RT
________ is the frequency factor.

A)k
B)A
C)e
D)E_a
E)R

Question 29

In general, as temperature goes up, reaction rate ________.

A)goes up if the reaction is exothermic
B)goes up if the reaction is endothermic
C)goes up regardless of whether the reaction is exothermic or endothermic
D)stays the same regardless of whether the reaction is exothermic or endothermic
E)stays the same if the reaction is first order

Question 30

Of the following, ________ will lower the activation energy for a reaction.

A)increasing the concentrations of reactants
B)raising the temperature of the reaction
C)adding a catalyst for the reaction
D)removing products as the reaction proceeds
E)increasing the pressure

Question 31

At elevated temperatures, methylisonitrile (CH₃NC)isomerizes to acetonitrile (CH₃CN): CH₃NC (g) → CH₃CN (g)
The reaction is first order in methylisonitrile. The attached graph shows data for the reaction obtained at 198.9 °C. The rate constant for the reaction is ________ s^-1.

A)-1.9 × 10⁴
B)+1.9 × 10⁴
C)-5.2 × 10^-5
D)+5.2 × 10^-5
E)+6.2

Question 32

The rate of a reaction depends on ________.

A)collision frequency
B)collision energy
C)collision orientation
D)all of the above
E)none of the above

Question 33

The primary source of the specificity of enzymes is ________.

A)their polarity, which matches that of their specific substrate
B)their delocalized electron cloud
C)their bonded transition metal, which is specific to the target substrate
D)their locations within the cell
E)their shape, which relates to the lock-and-key model

Question 34

The mechanism for formation of the product X is: A + B → C + D (slow)
B + D → X (fast)
The intermediate reactant in the reaction is ________.

A)A
B)B
C)C
D)D
E)X

Question 35

At elevated temperatures, methylisonitrile (CH₃NC)isomerizes to acetonitrile (CH₃CN): CH₃NC (g) → CH₃CN (g)
The dependence of the rate constant on temperature is studied and the graph below is prepared from the results. The energy of activation of this reaction is ________ kJ/mol.

A)160
B)1.6 × 10⁵
C)4.4 × 10^-7
D)4.4 × 10^-4
E)1.9 × 10⁴

Question 36

In general, as activation energy increases, reaction rate ________.

A)goes down if the reaction is exothermic
B)goes down if the reaction is endothermic
C)stays the same regardless of whether the reaction is exothermic or endothermic
D)goes down regardless of whether the reaction is exothermic or endothermic
E)none of the above

Question 37

The enzyme nitrogenase converts ________ into ________.

A)ammonia, urea
B)CO and unburned hydrocarbons, H₂O and CO₂
C)nitrogen, ammonia
D)nitrogen oxides, N₂ and O₂
E)nitroglycerine, nitric acid, and glycerine

Question 38

In the energy profile of a reaction, the species that exists at the maximum on the curve is called the ________.

A)product
B)activated complex
C)activation energy
D)enthalpy of reaction
E)atomic state

Question 39

The rate law of the overall reaction A + B → C
Is rate = k[A]². Which of the following will not increase the rate of the reaction?

A)increasing the concentration of reactant A
B)increasing the concentration of reactant B
C)increasing the temperature of the reaction
D)adding a catalyst for the reaction
E)All of these will increase the rate.

Question 40

A possible mechanism for the overall reaction Br₂ (g) + 2NO (g) → 2NOBr (g)
Is
NO (g) + Br₂ (g) NOBr₂ (g)(fast)
NOBr₂ (g) + NO (g) 2NOBr (slow)
The rate law for formation of NOBr based on this mechanism is rate = ________.

A)k₁[NO]^1/2
B)k₁[Br₂]^1/2
C)(k₂k₁/k^-1)[NO]²[Br₂]
D)(k₁/k^-1)²[NO]²
E)(k₂k₁/k^-1)[NO][Br₂]²

Question 41

At elevated temperatures, methylisonitrile (CH₃NC)isomerizes to acetonitrile (CH₃CN): CH₃NC (g) → CH₃CN (g)
At the start of the experiment, there are 0.200 mol of reactant (CH₃NC)and 0 mol of product (CH₃CN)in the reaction vessel. After 25 min of reaction, 0.108 mol of reactant (CH₃NC)remain. The average rate of decomposition of methyl isonitrile, CH₃NC, in this 25 min period is ________ mol/min.

A)3.7 × 10^-3
B)0.092
C)2.3
D)4.3 × 10^-3
E)0.54

Question 42

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g)→B(g). The following data are obtained for [A] as the reaction proceeds:
How many moles of B are present at 10 s?

A)0.011
B)0.220
C)0.110
D)0.014
E)1.4 × 10^-3

Question 43

The peroxydisulfate ion (S₂O₈^2-)reacts with the iodide ion in aqueous solution via the reaction:
S₂O₈^2- (aq) + 3I^- → 2SO₄ (aq)+ I₃^- (aq)
An aqueous solution containing 0.050 M of S₂O₈^2- ion and 0.072 M of I^- is prepared, and the progress of the reaction followed by measuring [I^-]. The data obtained is given in the table below.
The average rate of disappearance of I^- between 400.0 s and 800.0 s is ________ M/s.

A)2.8 × 10^-5
B)1.4 × 10^-5
C)5.8 × 10^-5
D)3.6 × 10⁴
E)2.6 × 10^-4

Question 44

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g)→B(g). The following data are obtained for [A] as the reaction proceeds:
The average rate of appearance of B between 20 s and 30 s is ________ mol/s.

A)+1.5 × 10^-3
B)+5.0 × 10^-4
C)-1.5 × 10^-3
D)+7.3 × 10^-3
E)-7.3 × 10^-3

Question 45

At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen: 2N₂O₅(g) → 4NO₂ (g) + O₂ (g)
When the rate of formation of NO₂ is 5.5 × 10^-4 M/s, the rate of decomposition of N₂O₅ is ________ M/s.

A)2.2 × 10^-3
B)1.4 × 10^-4
C)10.1 × 10^-4
D)2.8 × 10^-4
E)5.5 × 10^-4

Question 46

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g)→B(g). The following data are obtained for [A] as the reaction proceeds:
The average rate of disappearance of A between 20 s and 40 s is ________ mol/s.

A)8.5 × 10^-4
B)1.7 × 10^-3
C)590
D)7.1 × 10^-3
E)1.4 × 10^-3

Question 47

The peroxydisulfate ion (S₂O₈^2-)reacts with the iodide ion in aqueous solution via the reaction:
S₂O₈^2- (aq) + 3I^- → 2SO₄ (aq)+ I₃^- (aq)
An aqueous solution containing 0.050 M of S₂O₈^2- ion and 0.072 M of I^- is prepared, and the progress of the reaction followed by measuring [I^-]. The data obtained is given in the table below.
The average rate of disappearance of I^- between 1200.0 s and 1600.0 s is ________ M/s.

A)1.8 × 10^-5
B)1.2 × 10^-5
C)2.0 × 10^-5
D)5.0 × 10⁴
E)1.6 × 10^-4

Question 48

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g)→B(g). The following data are obtained for [A] as the reaction proceeds:
How many moles of B are present at 30 s?

A)2.4 × 10^-3
B)0.15
C)0.073
D)1.7 × 10^-3
E)0.051

Question 49

A reaction was found to be second order in carbon monoxide concentration. The rate of the reaction ________ if the [CO] is doubled, with everything else kept the same.

A)doubles
B)remains unchanged
C)triples
D)increases by a factor of 4
E)is reduced by a factor of 2

Question 50

The concentration of S₂O₈^2- remaining at 1600 s is ________ M.

A)0.036
B)0.014
C)0.043
D)0.064
E)0.029

Question 51

Consider the following reaction: A → 2C
The average rate of appearance of C is given by Δ[C]/Δt. Comparing the rate of appearance of C and the rate of disappearance of A, we get Δ[C]/Δt = ________ × (-Δ[A]/Δt).

A)+2
B)-1
C)+1
D)+1/2
E)-1/2

Question 52

The active site of nitrogenase is a cofactor that contains two transition metals. These transition metals are ________.

A)Cr and Mg
B)Mn and V
C)Os and Ir
D)Fe and Zn
E)Fe and Mo

Question 53

The concentration of S₂O₈^2- remaining at 400 s is ________ M.

A)+0.015
B)+0.035
C)-0.007
D)+0.045
E)+0.057

Question 54

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g)→B(g). The following data are obtained for [A] as the reaction proceeds:
The average rate of disappearance of A between 10 s and 20 s is ________ mol/s.

A)2.2 × 10^-3
B)1.1 × 10^-3
C)4.4 × 10^-3
D)454
E)9.90 × 10^-3

Question 55

The concentration of S₂O₈^2- remaining at 800 s is ________ M.

A)0.046
B)0.076
C)4.00 × 10^-3
D)0.015
E)0.041

Question 56

Nitrogen fixation is a difficult process because ________.

A)there is so little nitrogen in the atmosphere
B)nitrogen exists in the atmosphere primarily as its oxides which are very unreactive
C)nitrogen is very unreactive, largely due to its triple bond
D)of the extreme toxicity of nitrogen
E)of the high polarity of nitrogen molecules preventing them from dissolving in biological fluids, such as those inside cells

Question 57

The peroxydisulfate ion (S₂O₈^2-)reacts with the iodide ion in aqueous solution via the reaction:
S₂O₈^2- (aq) + 3I^- → 2SO₄ (aq)+ I₃^- (aq)
An aqueous solution containing 0.050 M of S₂O₈^2- ion and 0.072 M of I^- is prepared, and the progress of the reaction followed by measuring [I^-]. The data obtained is given in the table below.
The average rate of disappearance of I^- in the initial 400.0 s is ________ M/s.

A)6.00
B)3.8 × 10^-5
C)1.4 × 10^-4
D)2.7 × 10⁴
E)3.2 × 10^-4

Question 58

Consider the following reaction: 3A → 2B
The average rate of appearance of B is given by Δ[B]/Δt. Comparing the rate of appearance of B and the rate of disappearance of A, we get Δ[B]/Δt = ________ × (-Δ[A]/Δt).

A)-2/3
B)+2/3
C)-3/2
D)+1
E)+3/2

Question 59

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g)→B(g). The following data are obtained for [A] as the reaction proceeds:
The average rate disappearance of A between 20 s and 30 s is ________ mol/s.

A)5.0 × 10^-4
B)1.6 × 10^-2
C)1.5 × 10^-3
D)670
E)0.15

Question 60

Which substance in the reaction below either appears or disappears the fastest? 4NH₃ + 7O₂ → 4NO₂ + 6H₂O

A)NH₃
B)O₂
C)NO₂
D)H₂O
E)The rates of appearance/disappearance are the same for all of these.

Question 61

Of the following, only ________ is a valid unit for reaction rate.

A)M/s
B)mmol/mL
C)mol/g
D)g/L
E)atm/g

Question 62

The overall order of a reaction is 2. The units of the rate constant for the reaction are ________.

A)M/s
B)M^-1s^-1
C)1/s
D)1/M
E)s/M²

Question 63

The data in the table below were obtained for the reaction:
A + B → P
The order of the reaction in A is ________.

A)1
B)2
C)3
D)4
E)0

Question 64

A reaction was found to be zero order in A. Increasing the concentration of A by a factor of 3 will cause the reaction rate to ________.

A)remain constant
B)increase by a factor of 27
C)increase by a factor of 9
D)triple
E)decrease by a factor of the cube root of 3

Question 65

The overall order of a reaction is 1. The units of the rate constant for the reaction are ________.

A)M/s
B)M^-1s^-1
C)1/s
D)1/M
E)s/M²

Question 66

The data in the table below were obtained for the reaction:
A + B → P
The overall order of the reaction is ________.

A)1
B)2
C)3
D)4
E)0

Question 67

A second-order reaction has a half-life of 12 s when the initial concentration of reactant is 0.98 M. The rate constant for this reaction is ________ M^-1s^-1.

A)12
B)2.0 × 10^-2
C)8.5 × 10^-2
D)4.3 × 10^-2
E)4.3

Question 68

For a first-order reaction, a plot of ________ versus ________ is linear.

A)ln [A]_t,
B)ln [A]_t, t
C) , t
D)[A]_t, t
E)t,

Question 69

A reaction was found to be third order in A. Increasing the concentration of A by a factor of 3 will cause the reaction rate to ________.

A)remain constant
B)increase by a factor of 27
C)increase by a factor of 9
D)triple
E)decrease by a factor of the cube root of 3

Question 70

The graph shown below depicts the relationship between concentration and time for the following chemical reaction. The slope of this line is equal to ________.

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

Question 71

If the rate law for the reaction 2A + 3B → products
Is first order in A and second order in B, then the rate law is rate = ________.

A)k[A][B]
B)k[A]²[B]³
C)k[A][B]²
D)k[A]²[B]
E)k[A]²[B]²

Question 72

The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.13 M, it takes ________ min for it to decrease to 0.085 M.

A)12
B)10.
C)8.0
D)11
E)7.0

Question 73

A second-order reaction has a half-life of 18 s when the initial concentration of reactant is 0.71 M. The rate constant for this reaction is ________ M^-1s^-1.

A)7.8 × 10^-2
B)3.8 × 10^-2
C)2.0 × 10^-2
D)1.3
E)18

Question 74

The reaction below is first order in [H₂O₂]: 2H₂O₂ (l) → 2H₂O (l) + O₂ (g)
A solution originally at 0.600 M H₂O₂ is found to be 0.075 M after 54 min. The half-life for this reaction is ________ min.

A)6.8
B)18
C)14
D)28
E)54

Question 75

If the rate law for the reaction 2A + 3B → products
Is second order in A and first order in B, then the rate law is rate = ________.

A)k[A][B]
B)k[A]²[B]³
C)k[A][B]²
D)k[A]²[B]
E)k[A]²[B]²

Question 76

The following reaction occurs in aqueous solution: NH₄⁺ (aq) + NO₂^- → N₂ (g) + 2H₂O (l)
The data below is obtained at 25 °C. The order of the reaction in NH₄⁺ is ________.

A)-2
B)-1
C)+2
D)+1
E)0

Question 77

The data in the table below were obtained for the reaction:
A + B → P
The order of the reaction in B is ________.

A)1
B)2
C)3
D)4
E)0

Question 78

The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.085 M, it takes ________ min for it to decrease to 0.055 M.

A)8.2
B)11
C)3.6
D)0.048
E)8.4

Question 79

The kinetics of the reaction below were studied and it was determined that the reaction rate did not change when the concentration of B was tripled. The reaction is ________ order in B. A + B → P

A)zero
B)first
C)second
D)third
E)one-half

Question 80

The kinetics of the reaction below were studied and it was determined that the reaction rate increased by a factor of 9 when the concentration of B was tripled. The reaction is ________ order in B. A + B → P

A)zero
B)first
C)second
D)third
E)one-half