7246754
Pregunta 1
Pregunta
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.
Respuesta
-
A) 1.1 × 10-4
-
B) 2.2 × 10-4
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C) 2.8 × 10-4
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D) 4.4 × 10-4
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E) 5.5 × 10-4
Pregunta 2
Pregunta
Which one of the following is not a valid expression for the rate of the reaction below?
4NH3 + 7O2 → 4NO2 + 6H2O
Respuesta
-
A)
-
B)
-
C)
-
D)
-
E) All of the above are valid expressions of the reaction rate.
Pregunta 3
Pregunta
The rate law of a reaction is rate = k[D][X]. The units of the rate constant are __________.
Respuesta
-
A) mol L-1s-1
-
B) L mol-1s-1
-
C) mol2 L-2s-1
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D) mol L-1s-2
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E) L2 mol -2s-1
Pregunta 4
Pregunta
The rate law for this reaction is rate = __________.
Respuesta
-
A) k[A][B]
-
B) k[P]
-
C) k[A]2[B]
-
D) k[A]2[B]2
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E) k[A]2
Pregunta 5
Pregunta
Under constant conditions, the half-life of a first-order reaction __________.
Respuesta
-
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
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E) All of the above are correct.
Pregunta 6
Pregunta
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.
Respuesta
-
A) 0.096
-
B) 0.65
-
C) 0.81
-
D) 1.2
-
E) 0.54
Pregunta 7
Pregunta
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 __________.
Respuesta
-
A) 65 minutes
-
B) 120 minutes
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C) 145 minutes
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D) 180 minutes
-
E) 198 minutes
Pregunta 8
Pregunta
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.
Respuesta
-
A) 2.4
-
B) 0.27
-
C) 0.24
-
D) 1.4
-
E) 1.2 × 10-2
Pregunta 9
Pregunta
The rate constant for this reaction is __________ s-1.
Respuesta
-
A) 6.9 × 10-2
-
B) 3.0 × 10-2
-
C) 14
-
D) 0.46
-
E) 4.0 × 102
Pregunta 10
Pregunta
The concentration of A is __________ M after 40.0 s.
Respuesta
-
A) 1.3 × 10-2
-
B) 1.2
-
C) 0.17
-
D) 3.5 × 10-4
-
E) 0.025
Pregunta 11
Pregunta
The rate constant of a first-order process that has a half-life of 225 s is __________s-1.
Respuesta
-
A) 0.693
-
B) 3.08 × 10-3
-
C) 1.25
-
D) 12.5
-
E) 4.44 × 10-3
Pregunta 12
Pregunta
One difference between first- and second-order reactions is that __________.
Respuesta
-
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
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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.
Pregunta 13
Pregunta
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.
Respuesta
-
A) -1.9 × 104
-
B) +1.9 × 104
-
C) -5.2 × 10-5
-
D) +5.2 × 10-5
-
E) +6.2
Pregunta 14
Pregunta
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 = __________.
Respuesta
-
A) k[N2O5]2
-
B)
-
C) k[N2O5]
-
D)
-
E)2k[N2O5]
Pregunta 15
Pregunta
As the temperature of a reaction is increased, the rate of the reaction increases because the __________.
Respuesta
-
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
Pregunta 16
Pregunta
The rate of a reaction depends on __________.
Respuesta
-
A) collision frequency
-
B) collision energy
-
C) collision orientation
-
D) all of the above
-
E) none of the above
Pregunta 17
Pregunta
Which energy difference in the energy profile below corresponds to the activation energy for the forward reaction?
Respuesta
-
A) x
-
B) y
-
C) x + y
-
D) x - y
-
E) y – x
Pregunta 18
Pregunta
In the energy profile of a reaction, the species that exists at the maximum on the curve is called the __________.
Respuesta
-
A) product
-
B) activated complex
-
C) activation energy
-
D) enthalpy of reaction
-
E) atomic state
Pregunta 19
Pregunta
In general, as temperature goes up, reaction rate __________.
Respuesta
-
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
Pregunta 20
Pregunta
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.
Respuesta
-
A) 160
-
B) 1.6 × 105
-
C) 4.4 × 10-7
-
D) 4.4 × 10-4
-
E) 1.9 × 104
Pregunta 21
Pregunta
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 __________.
Respuesta
-
A) A
-
B) B
-
C) C
-
D) D
-
E) X
Pregunta 22
Pregunta
Which of the following is true?
Respuesta
-
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.
Pregunta 23
Pregunta
Of the following, __________ will lower the activation energy for a reaction.
Respuesta
-
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
Pregunta 24
Pregunta
A catalyst can increase the rate of a reaction __________.
Respuesta
-
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.
Pregunta 25
Pregunta
Nitrogen fixation is a difficult process because __________.
Respuesta
-
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
Pregunta 26
Pregunta
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).
Respuesta
-
A) -2/3
-
B) +2/3
-
C) -3/2
-
D) +1
-
E) +3/2
Pregunta 27
Pregunta
Which substance in the reaction below either appears or disappears the fastest?
4NH3 + 7O2 → 4NO2 + 6H2O
Respuesta
-
A) NH3
-
B) O2
-
C) NO2
-
D) H2O
-
E) The rates of appearance/disappearance are the same for all of these.
Pregunta 28
Pregunta
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.
Respuesta
-
A) 2.2 × 10-3
-
B) 1.1 × 10-3
-
C) 4.4 × 10-3
-
D) 454
-
E) 9.90 × 10-3
Pregunta 29
Pregunta
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.
Respuesta
-
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
Pregunta 30
Pregunta
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.
Respuesta
-
A) doubles
-
B) remains unchanged
-
C) triples
-
D) increases by a factor of 4
-
E) is reduced by a factor of 2
Pregunta 31
Pregunta
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.
Respuesta
-
A) 8.2
-
B) 11
-
C) 3.6
-
D) 0.048
-
E) 8.4
Pregunta 32
Pregunta
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.
Respuesta
-
A) 7.8 × 10-2
-
B) 3.8 × 10-2
-
C) 2.0 × 10-2
-
D) 1.3
-
E) 18
Pregunta 33
Pregunta
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.
Respuesta
-
A) 3.85
-
B) 0.0650
-
C) 0.0169
-
D) 0.260
-
E) 0.0860
Pregunta 34
Pregunta
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.
Respuesta
-
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
Pregunta 35
Pregunta
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 __________.
Respuesta
-
A) 0.0276 M
-
B) 0.0324 M
-
C) 0.0353 M
-
D) 0.0480 M
-
E) 0.0402 M
Pregunta 36
Pregunta
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?
Respuesta
-
A) 9.56 × 103
-
B) 2.85 × 104
-
C) 576
-
D) 4.33 × 1087
-
E) 1.36 × 102
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