Deck 14: Chemical Kinetics

Question 1

The combustion of ethylene proceeds by the reaction C₂H₄ (g) + 3O₂ (g) →2CO₂ (g) + 2H₂O (g)
When the rate of disappearance of O₂ is 0.28 M s^{- 1}, the rate of appearance of CO₂ is _ _ M s^{- 1}.

A) 0.84
B) 0.42
C) 0.56
D) 0.093
E) 0.19

Answer 1

0.19

Question 2

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

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

Answer 2

1.2 × 10^{- 2}

Question 3

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

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

Answer 3

activated complex

Question 4

The rate law of the overall reaction is rate = k[A]². Which of the following will not increase the rate of the reaction?

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

Question 5

The primary source of the specificity of enzymes is .

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

Question 6

Nitrogen fixation is a difficult process because .

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

Question 7

A particular first- order reaction has a rate constant of 1.35 × 10² s^{- 1} at 25°C. What is the magnitude of k at 75°C if E_a = 85.6 kJ/mol?

A) 1.36 × 10²
B) 3.85 × 10⁶
C) 670
D) 1.93 × 10⁴
E) 3.47 × 10⁴

Question 8

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

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

Question 9

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

Question 10

The reaction A - B is first order in [A]. Consider the following data.
The half- life of this reaction is s.

A) 0.14
B) 4.9
C) 0.97
D) 3.0
E) 7.1

Question 11

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

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

Question 12

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

A) 3.1 × 10^{- 3}
B) 0.013
C) 0.14
D) 3.0
E) 0.030

Question 13

SO₂Cl₂ decomposes in the gas phase by the reaction SO₂Cl₂ (g) →SO₂ (g) + Cl₂ (g)
The reaction is first order in SO₂Cl₂ and the rate constant is 3.0 × 10^{- 6} s^{- 1}at 600 K. A vessel is charged with 2.4 atm of SO₂Cl₂ at 600 K. The partial pressure of SO₂Cl₂ at 3.0 × 10⁵ s is
Atm)

A) 1.4 × 10⁵
B) 0.76
C) 0.29
D) 2.2
E) 0.98

Question 14

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 15

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

Question 16

SO₂Cl₂ decomposes in the gas phase by the reaction SO₂Cl₂ (g) →SO₂ (g) + Cl₂ (g)
The reaction is first order in SO₂Cl₂ and the rate constant is 3.0 × 10^{- 6} s^{- 1}at 600 K. A vessel is charged with 3.3 atm of SO₂Cl₂ at 600 K. The partial pressure of SO₂ at 3.0 × 10⁵ s is _ _ atm.

A) 2.0
B) 3.7
C) 3.0
D) 2.1
E) 1.3

Question 17

The isomerization of methylisonitrile to acetonitrile CH₃NC (g) → CH₃CN (g)
Is first order in CH₃NC. The half life of the reaction is 1.60 × 10⁵ s at 444 K. The rate constant when the initial [CH₃NC] is 0.030 M is _ s^{- 1}.

A) 2.08 × 10^{- 4}
B) 4.80 × 10³
C) 7.10 × 10⁷
D) 2.31 × 10⁵
E) 4.33 × 10^{- 6}

Question 18

The elementary reaction
2NO₂ (g) → 2NO (g) + O₂ (g)
Is second order in NO₂ and the rate constant at 501 K is 7.93 × 10^{- 3} M^{- 1}s^{- 1}. The reaction half- life at this temperature when [NO₂]₀ = 0.450 M is s.

A) 126
B) 0.011
C) 3.6 × 10^{- 3}
D) 280
E) 87

Question 19

The reaction
2NO₂ → 2NO + O₂
Follows second- order kinetics. At 300°C, [NO₂] drops from 0.0100- to 0.00650- M in 100 s. The rate constant for the reaction is _ M^{- 1}s^{- 1}.

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

Question 20

Of the units below, are appropriate for a first- order reaction rate constant.

A) s^{- 1}
B) mol/L
C) L mol^{- 1} s^{- 1}
D) M s^{- 1}
E) ._M- 1 _s- 1

Question 21

In general, as temperature goes up, reaction rate .

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

Question 22

The combustion of ethylene proceeds by the reaction C₂H₄ (g) + 3O₂ (g) → 2CO₂ (g) + 2H₂O (g)
When the rate of disappearance of O₂ is 0.23 M s^{- 1}, the rate of disappearance of C₂H₄ is
M s^{- 1}.

A) 0.46
B) 0.15
C) 0.077
D) 0.35
E) 0.69

Question 23

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

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

Question 24

In the Arrhenius equation, _{k = Ae}- Ea/RT Is the frequency factor.

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

Question 25

The rate constant of a first- order process that has a half- life of 225 s is s^{- 1}.

A) 3.08 × 10^{- 3}
B) 0.693
C) 1.25
D) 12.5
E) 4.44 × 10^{- 3}

Question 26

are used in automotive catalytic converters.

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

Question 27

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

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

Question 28

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

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

Question 29

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

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

Question 30

The rate of disappearance of HBr in the gas phase reaction 2HBr (g) → H₂ (g) + Br₂ (g)
Is 0.190 M s^{- 1} at 150°C. The rate of reaction is M s^{- 1}.

A) 2.63
B) 0.086
C) 0.0361
D) 0.095
E) 0.380

Question 31

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) 2
C) 1
D) 3
E) 0

Question 32

The rate of disappearance of HBr in the gas phase reaction 2HBr (g) →H₂ (g) + Br₂ (g)
Is 0.301 M s^{- 1} at 150°C. The rate of appearance of Br₂ is M s^{- 1}.

A) 0.549
B) 1.66
C) 0.602
D) 0.151
E) 0.0906

Question 33

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) 2.21
E) 42.0

Question 34

At elevated temperatures, methylisonitrile (CH₃NC) isomerizes to acetonitrile (CH₃CN):
CH₃NC (g) → CH₃3CN (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) +5.2 × 10^{- 5}
B) +6.2
C) +1.9 × 10⁴
D) - 5.2 × 10^{- 5}
E) - 1.9 × 10⁴

Question 35

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

Question 36

The half- life of a first- order reaction .

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

Question 37

The isomerization of methylisonitrile to acetonitrile CH₃NC (g) → CH₃CN (g)
Is first order in CH₃NC. The rate constant for the reaction is 9.45 × 10^{- 5} s^{- 1} at 478 K. The half- life of the reaction when the initial [CH₃NC] is 0.030 M is s.

A) 3.53E × 10⁵
B) 1.36 × 10^{- 4}
C) 7.33 × 10³
D) 1.06 × 10⁴
E) 5.29 × 10³

Question 38

A particular first- order reaction has a rate constant of 1.35 × 10² s^{- 1} at 25°C. What is the magnitude of k at 95°C if E_a = 55.5 kJ/mol?

A) 4.33 × 10⁸⁷
B) 1.36 × 10²
C) 576
D) 2.85 × 10⁴
E) 9.60 × 10³

Question 39

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) 4.6
B) 115
C) 230
D) 713
E) 1.15 × 10⁴

Question 40

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

A) the rate of a first- order reaction does not depend on reactant concentrations; the rate of a second- order reaction does depend on reactant concentrations
B) a first- order reaction can be catalyzed; a second- order reaction cannot be catalyzed
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) the half- life of a first- order reaction depends on [A]₀; the half- life of a second- order reaction does not depend on [A]₀
E) 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

Question 41

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

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

Question 42

Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction:
2NO₂ → 2NO + O₂
In a particular experiment at 300°C, [NO₂] drops from 0.0100 to 0.00650 M in 100 s. The rate of disappearance of NO₂ for this period is _ M/s.

A) 0.35
B) 1.8 × 10^{- 3}
C) 3.5 × 10^{- 3}
D) 7.0 × 10^{- 3}
E) 3.5 × 10^{- 5}

Question 43

For the reaction aA + Bb → cC + dD the rate law is .

Question 44

The relationship of absorbed light to the concentration of the substance absorbing the light is governed by .

Question 45

The number of molecules that participate as reactants defines the of the reaction.

Question 46

The rate of a reaction depends on _.

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

Question 47

The rate law for a reaction is
Rate = k [A][B]²
Which one of the following statements is false?

A) The reaction is second order overall.
B) The reaction is second order in B.
C) k is the reaction rate constant
D) If [B] is doubled, the reaction rate will increase by a factor of 4.
E) The reaction is first order in A.

Question 48

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

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

Question 49

The minimum energy to initiate a chemical reaction is the .

Question 50

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 51

The following reaction is second order in [A] and the rate constant is 0.039 M^{- 1}s^{- 1}:
A - B
The concentration of A was 0.30 M at 23s. The initial concentration of A was _ M.

A) 2.4
B) 1.2 × 10^{- 2}
C) 3.7
D) 0.41
E) 0.27

Question 52

The overall reactions and rate laws for several reactions are given below. Of these, only _ could represent an elementary step.

A)
B)
C)
D)
E)

Question 53

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. If the reaction is initiated with 0.058 mol in a 1.00- L vessel, how many moles remain after 151 s?

A) 0.055
B) 2.0 × 10³
C) 0.028
D) 0.060
E) 12

Question 54

The mechanism for formation of the product X is:

The intermediate reactant in the reaction is .

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

Question 55

A catalyst can increase the rate of a reaction .

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

Question 56

The enzyme nitrogenase converts _ _ into _.

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

Question 57

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 58

The earth's ozone layer is located in the .

Question 59

Reaction rate data obey an equation devised by _ .

Question 60

For the elementary reaction the molecularity of the reaction is , and the rate law is rate = .

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

Question 61

The average rate of disappearance of I^- between 400 s and 800 s is M/s.

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

Question 62

If the rate law for the reaction is first order in A and second order in B, then the rate law is rate = .

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

Question 63

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

Question 64

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

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

Question 65

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

Question 66

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^{- 1}s^{- 1}.

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

Question 67

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

Question 68

The rate constant for a particular second- order reaction is 0.47 M^{- 1}s^{- 1}. If the initial concentration of reactant is 0.25 mol/L, it takes s for the concentration to decrease to 0.13 mol/L.

A) 1.7
B) 1.4
C) 7.9
D) 0.13
E) 3.7

Question 69

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

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

Question 70

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

Question 71

If a rate law is second order (reactant) , doubling the reactant _ _ the reaction rate.

Question 72

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

Question 73

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) is reduced by a factor of 2.
D) increases by a factor of 4
E) triples

Question 74

The rate constant for a second- order reaction is 0.13 M^{- 1}s^{- 1}. If the initial concentration of reactant is 0.26 mol/L, it takes s for the concentration to decrease to 0.13 mol/L.

A) 1.0
B) 0.017
C) 30
D) 4.4 × 10^{- 3}
E) 0.50

Question 75

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

Question 76

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 77

Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction:
2NO₂ → 2NO + O₂
In a particular experiment at 300°C, [NO₂] drops from 0.0100 to 0.00650 M in 100 s. The rate of appearance of O₂ for this period is _ M/s.

A) 7.0 × 10^{- 5}
B) 3.5 × 10^{- 3}
C) 7.0 × 10^{- 3}
D) 3.5 × 10^{- 5}
E) 1.8 × 10^{- 5}

Question 78

The average rate disappearance of A between 20 s and 30 s is mol/s.

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

Question 79

Reaction rates are affected by reactant concentrations and temperature. This is accounted for by the .

Question 80

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

A) M/s
B) 1/M
C) 1/s
D) M^{- 1}s^{- 1}
E) s/M²