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Chapter 12- Kinetics

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Originally chapter 14
Dawn G
Quiz by Dawn G, updated more than 1 year ago
Dawn G
Created by Dawn G over 7 years ago
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Question 1

Question
At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen: 2N2O5(g) → 4NO2 (g) + O2 (g) When the rate of formation of O2 is 2.2 × 10-4 M/s, the rate of decomposition of N2O5 is __________ M/s.
Answer
  • A) 1.1 × 10-4
  • B) 2.2 × 10-4
  • C) 2.8 × 10-4
  • D) 4.4 × 10-4
  • E) 5.5 × 10-4

Question 2

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

Question 3

Question
The rate law of a reaction is rate = k[D][X]. The units of the rate constant are __________.
Answer
  • 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 4

Question
The rate law for this reaction is rate = __________.
Image:
46dfe836-a991-4540-9b6b-0ef9208054fe (image/png)
Answer
  • A) k[A][B]
  • B) k[P]
  • C) k[A]2[B]
  • D) k[A]2[B]2
  • E) k[A]2

Question 5

Question
Under constant conditions, the half-life of a first-order reaction __________.
Answer
  • 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 6

Question
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.
Answer
  • A) 0.096
  • B) 0.65
  • C) 0.81
  • D) 1.2
  • E) 0.54

Question 7

Question
A compound decomposes by a first-order process. If 25.0% of the compound decomposes in 60.0 minutes, the half-life of the compound is __________.
Answer
  • A) 65 minutes
  • B) 120 minutes
  • C) 145 minutes
  • D) 180 minutes
  • E) 198 minutes

Question 8

Question
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.
Answer
  • A) 2.4
  • B) 0.27
  • C) 0.24
  • D) 1.4
  • E) 1.2 × 10-2

Question 9

Question
The rate constant for this reaction is __________ s-1.
Image:
3d329de9-c665-4f43-a3c3-a4d64f0bc377 (image/png)
Answer
  • A) 6.9 × 10-2
  • B) 3.0 × 10-2
  • C) 14
  • D) 0.46
  • E) 4.0 × 102

Question 10

Question
The concentration of A is __________ M after 40.0 s.
Image:
0b378ba5-cd08-48fc-a9c2-1831b20fadf8 (image/png)
Answer
  • A) 1.3 × 10-2
  • B) 1.2
  • C) 0.17
  • D) 3.5 × 10-4
  • E) 0.025

Question 11

Question
The rate constant of a first-order process that has a half-life of 225 s is __________s-1.
Answer
  • A) 0.693
  • B) 3.08 × 10-3
  • C) 1.25
  • D) 12.5
  • E) 4.44 × 10-3

Question 12

Question
One difference between first- and second-order reactions is that __________.
Answer
  • 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 13

Question
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.
Image:
060d1692-876f-4ecb-8037-1a4350a05724 (image/png)
Answer
  • A) -1.9 × 104
  • B) +1.9 × 104
  • C) -5.2 × 10-5
  • D) +5.2 × 10-5
  • E) +6.2

Question 14

Question
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 = __________.
Answer

Question 15

Question
As the temperature of a reaction is increased, the rate of the reaction increases because the __________.
Answer
  • 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 16

Question
The rate of a reaction depends on __________.
Answer
  • A) collision frequency
  • B) collision energy
  • C) collision orientation
  • D) all of the above
  • E) none of the above

Question 17

Question
Which energy difference in the energy profile below corresponds to the activation energy for the forward reaction?
Image:
b2d05494-b416-4bbc-a4f8-ff2e9868a143 (image/png)
Answer
  • A) x
  • B) y
  • C) x + y
  • D) x - y
  • E) y – x

Question 18

Question
In the energy profile of a reaction, the species that exists at the maximum on the curve is called the __________.
Answer
  • A) product
  • B) activated complex
  • C) activation energy
  • D) enthalpy of reaction
  • E) atomic state

Question 19

Question
In general, as temperature goes up, reaction rate __________.
Answer
  • 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 20

Question
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.
Image:
6dace361-0d7d-48e4-806a-a810e895da5b (image/png)
Answer
  • A) 160
  • B) 1.6 × 105
  • C) 4.4 × 10-7
  • D) 4.4 × 10-4
  • E) 1.9 × 104

Question 21

Question
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 __________.
Answer
  • A) A
  • B) B
  • C) C
  • D) D
  • E) X

Question 22

Question
Which of the following is true?
Answer
  • 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

Question
Of the following, __________ will lower the activation energy for a reaction.
Answer
  • 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 24

Question
A catalyst can increase the rate of a reaction __________.
Answer
  • A) by changing the value of the frequency factor (A)
  • B) by increasing the overall activation energy (Ea) 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 25

Question
Nitrogen fixation is a difficult process because __________.
Answer
  • 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 26

Question
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).
Answer
  • A) -2/3
  • B) +2/3
  • C) -3/2
  • D) +1
  • E) +3/2

Question 27

Question
Which substance in the reaction below either appears or disappears the fastest? 4NH3 + 7O2 → 4NO2 + 6H2O
Answer
  • A) NH3
  • B) O2
  • C) NO2
  • D) H2O
  • E) The rates of appearance/disappearance are the same for all of these.

Question 28

Question
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.
Image:
43779092-03b0-47fa-b3a5-fec87cd4b9ae (image/png)
Answer
  • A) 2.2 × 10-3
  • B) 1.1 × 10-3
  • C) 4.4 × 10-3
  • D) 454
  • E) 9.90 × 10-3

Question 29

Question
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.
Image:
b94755e6-98c0-4ae3-a239-f724cb1bf8a3 (image/png)
Answer
  • 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 30

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

Question 31

Question
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.
Answer
  • A) 8.2
  • B) 11
  • C) 3.6
  • D) 0.048
  • E) 8.4

Question 32

Question
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.
Answer
  • A) 7.8 × 10-2
  • B) 3.8 × 10-2
  • C) 2.0 × 10-2
  • D) 1.3
  • E) 18

Question 33

Question
The rate of disappearance of HBr in the gas phase reaction 2HBr (g) → H2 (g) + Br2 (g) is 0.130 Ms-1 at 150°C. The rate of reaction is __________ Ms-1.
Answer
  • A) 3.85
  • B) 0.0650
  • C) 0.0169
  • D) 0.260
  • E) 0.0860

Question 34

Question
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 0.00550 M in 100 s. The rate of appearance of O2 for this period is __________ M/s.
Answer
  • A) 2.3 × 10-5
  • B) 4.5 × 10-5
  • C) 9.0 × 10-5
  • D) 4.5 × 10-3
  • E) 9.0 × 10-3

Question 35

Question
The reaction 2NOBr (g) → 2 NO (g) + Br2 (g) is a second-order reaction with a rate constant of 0.80 M-1s-1 at 11°C. If the initial concentration of NOBr is 0.0440 M, the concentration of NOBr after 7.0 seconds is __________.
Answer
  • A) 0.0276 M
  • B) 0.0324 M
  • C) 0.0353 M
  • D) 0.0480 M
  • E) 0.0402 M

Question 36

Question
A particular first-order reaction has a rate constant of 1.35 × 102s-1 at 25.0°C. What is the magnitude of k at 95.0°C if Ea = 55.5 kJ/mol?
Answer
  • A) 9.56 × 103
  • B) 2.85 × 104
  • C) 576
  • D) 4.33 × 1087
  • E) 1.36 × 102
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