7246754
Questão 1
Questão
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.
Responda
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A) 1.1 × 10-4
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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
Questão 2
Questão
Which one of the following is not a valid expression for the rate of the reaction below?
4NH3 + 7O2 → 4NO2 + 6H2O
Responda
-
A)
-
B)
-
C)
-
D)
-
E) All of the above are valid expressions of the reaction rate.
Questão 3
Questão
The rate law of a reaction is rate = k[D][X]. The units of the rate constant are __________.
Responda
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A) mol L-1s-1
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B) L mol-1s-1
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C) mol2 L-2s-1
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D) mol L-1s-2
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E) L2 mol -2s-1
Questão 4
Questão
The rate law for this reaction is rate = __________.
Responda
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A) k[A][B]
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B) k[P]
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C) k[A]2[B]
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D) k[A]2[B]2
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E) k[A]2
Questão 5
Questão
Under constant conditions, the half-life of a first-order reaction __________.
Responda
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A) is the time necessary for the reactant concentration to drop to half its original value
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B) is constant
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C) can be calculated from the reaction rate constant
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D) does not depend on the initial reactant concentration
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E) All of the above are correct.
Questão 6
Questão
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.
Responda
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A) 0.096
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B) 0.65
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C) 0.81
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D) 1.2
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E) 0.54
Questão 7
Questão
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 __________.
Responda
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A) 65 minutes
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B) 120 minutes
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C) 145 minutes
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D) 180 minutes
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E) 198 minutes
Questão 8
Questão
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.
Responda
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A) 2.4
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B) 0.27
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C) 0.24
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D) 1.4
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E) 1.2 × 10-2
Questão 9
Questão
The rate constant for this reaction is __________ s-1.
Responda
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A) 6.9 × 10-2
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B) 3.0 × 10-2
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C) 14
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D) 0.46
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E) 4.0 × 102
Questão 10
Questão
The concentration of A is __________ M after 40.0 s.
Responda
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A) 1.3 × 10-2
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B) 1.2
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C) 0.17
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D) 3.5 × 10-4
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E) 0.025
Questão 11
Questão
The rate constant of a first-order process that has a half-life of 225 s is __________s-1.
Responda
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A) 0.693
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B) 3.08 × 10-3
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C) 1.25
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D) 12.5
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E) 4.44 × 10-3
Questão 12
Questão
One difference between first- and second-order reactions is that __________.
Responda
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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
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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
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D) a first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed
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E) None of the above are true.
Questão 13
Questão
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.
Responda
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A) -1.9 × 104
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B) +1.9 × 104
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C) -5.2 × 10-5
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D) +5.2 × 10-5
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E) +6.2
Questão 14
Questão
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 = __________.
Responda
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A) k[N2O5]2
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B)
-
C) k[N2O5]
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D)
-
E)2k[N2O5]
Questão 15
Questão
As the temperature of a reaction is increased, the rate of the reaction increases because the __________.
Responda
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A) reactant molecules collide less frequently
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B) reactant molecules collide more frequently and with greater energy per collision
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C) activation energy is lowered
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D) reactant molecules collide less frequently and with greater energy per collision
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E) reactant molecules collide more frequently with less energy per collision
Questão 16
Questão
The rate of a reaction depends on __________.
Responda
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A) collision frequency
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B) collision energy
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C) collision orientation
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D) all of the above
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E) none of the above
Questão 17
Questão
Which energy difference in the energy profile below corresponds to the activation energy for the forward reaction?
Responda
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A) x
-
B) y
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C) x + y
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D) x - y
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E) y – x
Questão 18
Questão
In the energy profile of a reaction, the species that exists at the maximum on the curve is called the __________.
Responda
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A) product
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B) activated complex
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C) activation energy
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D) enthalpy of reaction
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E) atomic state
Questão 19
Questão
In general, as temperature goes up, reaction rate __________.
Responda
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A) goes up if the reaction is exothermic
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B) goes up if the reaction is endothermic
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C) goes up regardless of whether the reaction is exothermic or endothermic
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D) stays the same regardless of whether the reaction is exothermic or endothermic
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E) stays the same if the reaction is first order
Questão 20
Questão
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.
Responda
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A) 160
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B) 1.6 × 105
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C) 4.4 × 10-7
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D) 4.4 × 10-4
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E) 1.9 × 104
Questão 21
Questão
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 __________.
Responda
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A) A
-
B) B
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C) C
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D) D
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E) X
Questão 22
Questão
Which of the following is true?
Responda
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A) If we know that a reaction is an elementary reaction, then we know its rate law.
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B) The rate-determining step of a reaction is the rate of the fastest elementary step of its mechanism.
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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.
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D) In a reaction mechanism, an intermediate is identical to an activated complex.
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E) All of the above statements are true.
Questão 23
Questão
Of the following, __________ will lower the activation energy for a reaction.
Responda
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A) increasing the concentrations of reactants
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B) raising the temperature of the reaction
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C) adding a catalyst for the reaction
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D) removing products as the reaction proceeds
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E) increasing the pressure
Questão 24
Questão
A catalyst can increase the rate of a reaction __________.
Responda
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A) by changing the value of the frequency factor (A)
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B) by increasing the overall activation energy (Ea) of the reaction
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C) by lowering the activation energy of the reverse reaction
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D) by providing an alternative pathway with a lower activation energy
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E) All of these are ways that a catalyst might act to increase the rate of reaction.
Questão 25
Questão
Nitrogen fixation is a difficult process because __________.
Responda
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A) there is so little nitrogen in the atmosphere
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B) nitrogen exists in the atmosphere primarily as its oxides which are very unreactive
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C) nitrogen is very unreactive, largely due to its triple bond
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D) of the extreme toxicity of nitrogen
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E) of the high polarity of nitrogen molecules preventing them from dissolving in biological fluids, such as those inside cells
Questão 26
Questão
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).
Responda
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A) -2/3
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B) +2/3
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C) -3/2
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D) +1
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E) +3/2
Questão 27
Questão
Which substance in the reaction below either appears or disappears the fastest?
4NH3 + 7O2 → 4NO2 + 6H2O
Responda
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A) NH3
-
B) O2
-
C) NO2
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D) H2O
-
E) The rates of appearance/disappearance are the same for all of these.
Questão 28
Questão
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.
Responda
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A) 2.2 × 10-3
-
B) 1.1 × 10-3
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C) 4.4 × 10-3
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D) 454
-
E) 9.90 × 10-3
Questão 29
Questão
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.
Responda
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A) +1.5 × 10-3
-
B) +5.0 × 10-4
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C) -1.5 × 10-3
-
D) +7.3 × 10-3
-
E) -7.3 × 10-3
Questão 30
Questão
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.
Responda
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A) doubles
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B) remains unchanged
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C) triples
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D) increases by a factor of 4
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E) is reduced by a factor of 2
Questão 31
Questão
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.
Responda
-
A) 8.2
-
B) 11
-
C) 3.6
-
D) 0.048
-
E) 8.4
Questão 32
Questão
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.
Responda
-
A) 7.8 × 10-2
-
B) 3.8 × 10-2
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C) 2.0 × 10-2
-
D) 1.3
-
E) 18
Questão 33
Questão
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.
Responda
-
A) 3.85
-
B) 0.0650
-
C) 0.0169
-
D) 0.260
-
E) 0.0860
Questão 34
Questão
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.
Responda
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A) 2.3 × 10-5
-
B) 4.5 × 10-5
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C) 9.0 × 10-5
-
D) 4.5 × 10-3
-
E) 9.0 × 10-3
Questão 35
Questão
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 __________.
Responda
-
A) 0.0276 M
-
B) 0.0324 M
-
C) 0.0353 M
-
D) 0.0480 M
-
E) 0.0402 M
Questão 36
Questão
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?
Responda
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A) 9.56 × 103
-
B) 2.85 × 104
-
C) 576
-
D) 4.33 × 1087
-
E) 1.36 × 102
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