33
15) The rate constant for a particular zero-order reaction is 0.075 M s-1. If the initial concentration of
reactant is 0.537 M it takes ________ s for the concentration to decrease to 0.100 M.
A) 5.8
B) -5.8
C) -0.047
D) 7.2
E) 0.040
16) The reaction A → B is first order in [A]. Consider the following data.
The rate constant for this reaction is ________ s-1.
A) 0.014
B) 0.030
C) 0.013
D) 3.0
E) 3.1 × 10-3
17) The reaction A → B is first order in [A]. Consider the following data.
The half-life of this reaction is ________ s.
A) 5.0
B) 0.97
C) 7.1
D) 3.0
E) 0.14
18) The rate constant of a first-order process that has a half-life of 462 s is ________ s–1.
A) 1.50 × 10-3
B) 3.20 × 102
C) 6.67 × 102
D) -1.08 × 10-3
E) 2.16 × 10-3
19) The following reaction is second order in [A] and the rate constant is 0.039 M-1s-1:
A → B
The concentration of A was 0.26 M at 28 s. The initial concentration of A was ________ M.
A) 0.36
B) 2.8
C) -1.2
D) -1.5
E) -0.83
20) A compound decomposes by a first-order process. If 17.0% of the compound decomposes in 30
minutes, the half-life of the compound is ________.
A) 112 minutes
B) 12 minutes
C) 8 minutes
D) 223 minutes
E) 56 minutes
21) 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) 1.06 × 104
B) 5.29 × 103
C) 3.53 × 105
D) 7.33 × 103
E) 1.36 × 10-4
22) The elementary reaction
2NO2 (g) → 2NO (g) + O2 (g)
is second order in NO2 and the rate constant at 660 K is 5.23 M-1s–1. The reaction half-life at this
temperature when [NO2]0 = 0.45 M is ________ s.
A) 2.4
B) 7.6
C) 0.19
D) 0.13
E) 0.42
23) The isomerization of methylisonitrile to acetonitrile
CH3NC (g) → CH3CN (g)
is first order in CH3NC. The half-life of the reaction is 2.70 × 104 s at 463 K. The rate constant when the
initial [CH3NC] is 0.030 M is ________ s–1.
A) 3.90 × 104
B) 1.23 × 10-3
C) 2.57 × 10-5
D) 8.10 × 102
E) 1.25 × 107
24) 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
0.072 mol in a 1.00-L vessel, how many moles remain after 151 s?
A) 0.067
B) 0.074
C) 0.035
D) 9.6
E) 1.6 × 103
25) 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-1at 600 K. A vessel is charged
with 3.6 atm of SO2Cl2 at 600 K. The partial pressure of SO2Cl2 at 3.0 × 105 s is ________ atm.
A) 0.85
B) 3.2
C) 1.5
D) 0.19
E) 9.3 × 104
26) The rate constant for a particular second-order reaction is 0.47 M-1s-1. If the initial concentration of
reactant is 0.25 mol/L, it takes ________ s for the concentration to decrease to 0.20 mol/L.
A) 2.1
B) 1.4
C) 1.0
D) 0.47
E) 0.20
27) 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 6.0 seconds is ________.
A) 0.0276 M
B) 0.0324 M
C) 0.0363 M
D) 0.0348 M
E) 0.0402 M
28) A first-order reaction has a rate constant of 0.33 min-1. It takes ________ min for the reactant
concentration to decrease from 0.13 M to 0.066 M.
A) 0.085
B) 0.13
C) 0.89
D) 2.4
E) 2.1
29) The initial concentration of reactant in a first-order reaction is 0.27 M. The rate constant for the
reaction is 0.75 s-1. What is the concentration (mol/L) of reactant after 1.8 s?
A) 6.0
B) 1.7
C) 0.070
D) 0.012
E) 1.0
30) The rate constant for a second-order reaction is 0.13 M-1s-1. If the initial concentration of reactant is
0.26 mol/L, it takes ________ s for the concentration to decrease to 0.07 mol/L.
A) 0.017
B) 1.4
C) 14
D) 80.
E) 10.
31) At elevated temperatures, nitrogen dioxide decomposes to nitrogen oxide and oxygen:
NO2 (g) → NO (g) + O2 (g)
The reaction is second order in NO2 with a rate constant of 0.543 M-1s-1at 300 °C. If the initial [NO2] is
0.260 M, it will take ________ s for the concentration to drop to 0.075 M.
A) 3.34
B) 0.0880
C) 2.29
D) 0.299
E) 17.5
32) A particular first-order reaction has a rate constant of 1.35 × 102 s-1 at 25.0 °C. What is the magnitude
of k at 65.0 °C if Ea = 55.5 kJ/mol?
A) 1.92 × 103
B) 1.95 × 104
C) 358
D) 3.48 × 1073
E) 1.35 × 102
33) A particular first-order reaction has a rate constant of 1.35 × 102 s-1 at 25.0 °C. What is the magnitude
of k at 75.0 °C if Ea = 55.3 kJ/mol?
A) 2.24 × 104
B) 3.34 × 103
C) 433
D) 2.49 × 106
E) 1.35 × 102
14.4 Short Answer Questions
1) The relationship of absorbed light to the concentration of the substance absorbing the light is governed
by ________.
2) For the reaction aA + Bb → cC + dD, the rate law is ________.
3) If a rate law is second order (reactant), doubling the reactant ________ the reaction rate.
4) The Earth’s ozone layer is located in the ________.
5) Reaction rates are affected by reactant concentrations and temperature. This is accounted for by the
________.
6) The minimum energy to initiate a chemical reaction is the ________.
7) Reaction rate data showing temperature dependence obey an equation devised by ________.
8) The number of molecules that participate as reactants defines the ________ of the reaction.
9) Elementary reactions involving the simultaneous collision of three molecules are ________.
10) A catalyst that is present in the same phase as the reacting molecules is called a(n) ________ catalyst.
11) A catalyst that is present in a different phase from the reacting molecules is called a(n) ________
catalyst.
12) The binding of molecules to the surface of a catalyst is referred to as ________.
13) The uptake of molecules into the interior of another substance is referred to as ________.
14.5 True/False Questions Questions
1) Rates of reaction can be positive or negative.
2) The instantaneous rate of a reaction can be read directly from the graph of molarity versus time at any
point on the graph.
3) The overall reaction order is the sum of the orders of each reactant in the rate law.
4) Units of the rate constant of a reaction are independent of the overall reaction order.
5) The concentration of reactants or products at any time during the reaction can be calculated from the
integrated rate law.
6) The rate of a second order reaction can depend on the concentrations of more than one reactant.
7) The half-life for a first order rate law depends on the starting concentration.
8) The rate limiting step in a reaction is the slowest step in the reaction sequence.
9) Heterogeneous catalysts have different phases from reactants.