Deck 14: Chemical Kinetics

Question 1

What is the rate constant (s^-1)for this reaction?

A)3.0 × 10^-2
B)14
C)0.46
D)4.0 × 10²
E)7.8 × 10^-2

Answer 1

7.8 × 10^-2

Question 2

What is the concentration (M)of [A] after 80.0 s?

A)4.06
B)7.8 × 10^-2
C)5.00 × 10^-3
D)4.06 × 10^-4
E)0.01

Answer 2

4.06 × 10^-4

Question 3

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

Answer 3

mol/L

Question 4

What is the order of the reaction with respect to ClO₂?

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

Question 5

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 6

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 7

The following reaction is second order in [A] and the rate constant is 0.025 : 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 8

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 9

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.

Question 10

The magnitude of the rate constant is ________.

A)5.56
B)0.278
C)13.2
D)42.0
E)2.21

Question 11

The reaction CH₃-N≡C → CH₃-C≡N
Is a first-order reaction.At If is 1.00 × 10^-3 initially, is ________ M after

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 12

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 13

Which of the following is correct regarding the overall order of the reaction?

A)the overall order is found by subtracting the individual orders for ClO₂ and OH^-, so it is 1 for this reaction
B)the overall order for this reaction is based on the individual order for OH^-, so it is 1
C)the overall order is found by adding the individual orders for ClO₂ and OH^-, so it is 3 for this reaction
D)the overall order for this reaction is based on the individual order for ClO₂, so it is 2
E)the overall order cannot be determined

Question 14

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

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

Question 15

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 16

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 17

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 18

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 19

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 20

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

Question 21

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 22

A catalyst can ________ the rate of a reaction by providing an alternative pathway with a ________ activation energy

A)decrease, higher
B)increase, lower
C)decrease, lower
D)increase, higher
E)decrease, constant

Question 23

The decomposition of [A] in solution at 55 °C proceeds via first order: A (aq)→ B (aq)
What is the rate law for the reaction?

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

Question 24

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 25

The enzyme ________ converts nitrogen into ammonia.

A)oxygenase
B)hydrogenase
C)oxidase
D)nitroglycerine
E)nitrogenase

Question 26

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 27

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 with greater energy
E)reactant molecules collide more frequently

Question 28

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. What is the rate constant (s^-1)for the reaction?

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

Question 29

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 30

A possible mechanism for the overall reaction Br₂ (g)+ 2NO (g)→ 2NOBr (g)
Is
Step 1)NO (g)+ Br₂ (g) NOBr₂ (g)(fast)
Step 2)NOBr₂ (g)+ NO (g) 2NOBr (slow)
What is the rate determining step for this reaction?

A)step 2
B)reverse of step 1
C)both steps 1 and 2
D)step 1
E)reverse of step 2

Question 31

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 32

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 33

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

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

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

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 36

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 37

________ are used in automotive catalytic converters.

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

Question 38

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 39

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 40

The decomposition of [A] in solution at 80 °C proceeds via the following reaction: A (aq)→ B (aq)
The dependence of the rate constant on temperature is studied and the graph below is prepared from the results. What is the energy of activation (kJ/mol)for this reaction?

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

Question 41

Fe and Mo are transition metals found in the cofactor active site of ________.

A)hydrogenase
B)nitrogenase
C)oxidase
D)nitroglycerine
E)oxygenase

Question 42

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 43

Consider the following reaction: A → B
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 =

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

Question 44

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 45

Which of the following statements describes why nitrogen fixation is a difficult process?

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

Question 46

What is the concentration (M)of S₂O₈^2- remaining at T=0?

A)0.072
B)0.022
C)0.15
D)0.050
E)no S₂O₈^2- is remaining at T=0

Question 47

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 48

How many moles of B are present at 40.s?

A)0.18
B)0.070
C)0.124
D)0.054
E)7.8 × 10^-3

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 800 s is ________ M.

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

Question 51

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 52

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 53

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 54

What is the average rate of disappearance (M/s)of I^- between 800.0 s and 1200.0 s?

A)2.8 × 10^-5
B)3.3 × 10^-5
C)5.8 × 10⁴
D)2.3 × 10^-5
E)2.6 × 10^-4

Question 55

What is the average rate of disappearance (M/s)of I^- in the initial 800.0 s?

A)2.8
B)2.8 × 10^-5
C)3.3 × 10^-5
D)2.6 × 10^-2
E)3.1 × 10⁴

Question 56

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

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

Question 57

What is the concentration (M)of S₂O₈^2- remaining at 1200 s?

A)+0.035
B)+0.038
C)-0.038
D)+0.012
E)-0.012

Question 58

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 59

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 60

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 61

It was determined experimentally that the reaction rate doubled when the concentration of B was doubled in the following reaction: A + B → C
The reaction is ________ order in B.

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

Question 62

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

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

Question 63

If the rate law for the reaction A + 3B → C + 2D
Is zero order in A and first order in B,then the rate law is

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

Question 64

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 65

The following reaction occurs in aqueous solution: NH₄⁺ (aq)+ NO₂^- (aq)→ 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 66

It was determined experimentally that the reaction rate remained the same when the concentration of A was doubled in the following reaction: A + B → C
The reaction is ________ order in A.

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

Question 67

What is the order of the reaction in B?

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

Question 68

What is the order of the reaction in A?

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

Question 69

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

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

Question 70

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

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 71

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 72

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 73

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 74

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 75

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 76

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 77

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 78

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

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

Question 79

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

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

Question 80

What is the overall order of the reaction?

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