5) The average rate of disappearance of A between 20 s and 40 s is __________ mol/s.
A) 8.5 × 10-4
B) 1.7 × 10-3
C) 590
D) 7.1 × 10-3
E) 1.4 × 10-3
6) The average rate of appearance of B between 20 s and 30 s is __________ mol/s.
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
7) The average rate disappearance of A between 20 s and 30 s is __________ mol/s.
A) 5.0 × 10-4
B) 1.6 × 10-2
C) 1.5 × 10-3
D) 670
E) 0.15
8) How many moles of B are present at 10 s?
A) 0.011
B) 0.220
C) 0.110
D) 0.014
E) 1.4 × 10-3
9) How many moles of B are present at 30 s?
A) 2.4 × 10-3
B) 0.15
C) 0.073
D) 1.7 × 10-3
E) 0.051
The peroxydisulfate ion (S2O82-) reacts with the iodide ion in aqueous solution via the reaction:
S2O82- (aq) + 3I– → 2SO4 (aq) + I3– (aq)
An aqueous solution containing 0.050 M of S2O82- ion and 0.072 M of I– is prepared, and the progress
of the reaction followed by measuring [I–]. The data obtained is given in the table below.
10) The average rate of disappearance of I– between 400.0 s and 800.0 s is __________ M/s.
A) 2.8 × 10-5
B) 1.4 × 10-5
C) 5.8 × 10-5
D) 3.6 × 104
E) 2.6 × 10-4
11) The average rate of disappearance of I– in the initial 400.0 s is __________ M/s.
A) 6.00
B) 3.8 × 10-5
C) 1.4 × 10-4
D) 2.7 × 104
E) 3.2 × 10-4
12) The average rate of disappearance of I– between 1200.0 s and 1600.0 s is __________ M/s.
A) 1.8 × 10-5
B) 1.2 × 10-5
C) 2.0 × 10-5
D) 5.0 × 104
E) 1.6 × 10-4
13) The concentration of S2O82- remaining at 400 s is __________ M.
A) +0.015
B) +0.035
C) -0.007
D) +0.045
E) +0.057
14) The concentration of S2O82- remaining at 800 s is __________ M.
A) 0.046
B) 0.076
C) 4.00 × 10-3
D) 0.015
E) 0.041
15) The concentration of S2O82- remaining at 1600 s is __________ M.
A) 0.036
B) 0.014
C) 0.043
D) 0.064
E) 0.029
16) At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen:
2N2O5(g) → 4NO2 (g) + O2 (g)
When the rate of formation of NO2 is 5.5 × 10-4 M/s, the rate of decomposition of N2O5 is ________
M/s.
A) 2.2 × 10-3
B) 1.4 × 10-4
C) 10.1 × 10-4
D) 2.8 × 10-4
E) 5.5 × 10-4
17) At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):
CH3NC (g) → CH3CN (g)
At the start of the experiment, there are 0.200 mol of reactant (CH3NC) and 0 mol of product (CH3CN)
in the reaction vessel. After 25 min of reaction, 0.108 mol of reactant (CH3NC) remain. The average
rate of decomposition of methyl isonitrile, CH3NC, in this 25 min period is __________ mol/min.
A) 3.7 × 10-3
B) 0.092
C) 2.3
D) 4.3 × 10-3
E) 0.54
18) 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) triples
D) increases by a factor of 4
E) is reduced by a factor of 2
19) If the rate law for the reaction
2A + 3B → products
is first order in A and second order in B, then the rate law is rate = __________.
A) k[A][B]
B) k[A]2[B]3
C) k[A][B]2
D) k[A]2[B]
E) k[A]2[B]2
20) If the rate law for the reaction
2A + 3B → products
is second order in A and first order in B, then the rate law is rate = __________.
A) k[A][B]
B) k[A]2[B]3
C) k[A][B]2
D) k[A]2[B]
E) k[A]2[B]2
21) The overall order of a reaction is 1. The units of the rate constant for the reaction are __________.
A) M/s
B) M-1s-1
C) 1/s
D) 1/M
E) s/M2
22) The overall order of a reaction is 2. The units of the rate constant for the reaction are __________.
A) M/s
B) M-1s-1
C) 1/s
D) 1/M
E) s/M2
23) 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
24) The kinetics of the reaction below were studied and it was determined that the reaction rate did not
change 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
25) A reaction was found to be third order in A. Increasing the concentration of A by a factor of 3 will
cause the reaction rate to __________.
A) remain constant
B) increase by a factor of 27
C) increase by a factor of 9
D) triple
E) decrease by a factor of the cube root of 3
26) A reaction was found to be zero order in A. Increasing the concentration of A by a factor of 3 will
cause the reaction rate to __________.
A) remain constant
B) increase by a factor of 27
C) increase by a factor of 9
D) triple
E) decrease by a factor of the cube root of 3
The data in the table below were obtained for the reaction:
A + B → P
27) The order of the reaction in A is __________.
A) 1
B) 2
C) 3
D) 4
E) 0
28) The order of the reaction in B is __________.
A) 1
B) 2
C) 3
D) 4
E) 0
29) The overall order of the reaction is __________.
A) 1
B) 2
C) 3
D) 4
E) 0
30) The following reaction occurs in aqueous solution:
NH4+ (aq) + NO2– → N2 (g) + 2H2O (l)
The data below is obtained at 25°C.
The order of the reaction in NH4+ is __________.
A) -2
B) -1
C) +2
D) +1
E) 0
31) For a first-order reaction, a plot of __________ versus __________ is linear.
A) ln [A]t,
l
t
B) ln [A]t, t
C)
t
1,t
A
D) [A]t, t
E)
t
l
t, A
32) 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.
A) 8.2
B) 11
C) 3.6
D) 0.048
E) 8.4
33) The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.13 M, it
takes __________ min for it to decrease to 0.085 M.
A) 12
B) 10
C) 8.0
D) 11
E) 7.0
34) 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) k
B) -1/k
C) ln[A]o
D) -k
E) 1/k
35) 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) 6.8
B) 18
C) 14
D) 28
E) 54
36) 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.
A) 7.8 × 10-2
B) 3.8 × 10-2
C) 2.0 × 10-2
D) 1.3
E) 18
37) A second-order reaction has a half-life of 12 s when the initial concentration of reactant is 0.98 M.
The rate constant for this reaction is __________ M-1s-1.
A) 12
B) 2.0 x 10-2
C) 8.5 × 10-2
D) 4.3 x 10-2
E) 4.3
14.3 Algorithmic Questions
1) The rate of disappearance of HBr in the gas phase reaction
2HBr (g) → H2 (g) + Br2 (g)
is 0.301 Ms-1 at 150°C. The rate of appearance of Br2 is __________ Ms-1.
A) 1.66
B) 0.151
C) 0.0906
D) 0.602
E) 0.549
2) 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.
A) 3.85
B) 0.0650
C) 0.0169
D) 0.260
E) 0.0860
3) 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 Ms-1, the rate of appearance of CO2 is __________ Ms-1.
A) 0.19
B) 0.093
C) 0.84
D) 0.42
E) 0.56
4) 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 Ms-1, the rate of disappearance of C2H4 is __________
Ms-1.
A) 0.15
B) 0.077
C) 0.69
D) 0.35
E) 0.46
5) 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.
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
6) At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):
CH3NC (g) → CH3CN (g)
At the start of an experiment, there are 0.200 mol of reactant and 0 mol of product in the reaction vessel.
After 25 min, 0.106 mol of reactant (CH3NC) remain. There are __________ mol of product (CH3CN)
in the reaction vessel.
A) 0.022
B) 0.106
C) 0.200
D) 0.306
E) 0.094
7) The isomerization of methylisonitrile to acetonitrile
CH3NC (g) → CH3CN (g)
is first order in CH3NC. The rate constant for the reaction is 9.45 × 10-5s-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) 3.53E × 105
D) 7.33 × 103
E) 1.36 × 10-4
8) The elementary reaction
2NO2 (g) → 2NO (g) + O2 (g)
is second order in NO2 and the rate constant at 501 K is 7.93 × 10-3M-1s-1. The reaction half-life at this
temperature when [NO2]0= 0.45 M is __________ s.
A) 3.6 × 10-3
B) 0.011
C) 126
D) 87
E) 280
9) The isomerization of methylisonitrile to acetonitrile
CH3NC (g) → CH3CN (g)
is first order in CH3NC. The half life of the reaction is 5.20 × 101 s at 545 K. The rate constant when the
initial [CH3NC] is 0.030 M is __________ s-1.
A) 75.1
B) 0.641
C) 0.0133
D) 1.56
E) 2.84 × 104
10) 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 × 10-3s-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) 0.060
C) 0.028
D) 12
E) 2.0 × 103
11) 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 × 10-6s-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) 0.76
B) 2.2
C) 0.98
D) 0.29
E) 1.4 × 105
12) The rate constant for a particular second-order reaction is 0.47M-1s-1. If the initial concentration of
reactant is 0.25 mol/L, it takes __________ s for the concentration to decrease to 0.080 mol/L.
A) 18
B) 1.4
C) 8.5
D) 4.0
E) 0.08
13) 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 __________.
A) 0.0276 M
B) 0.0324 M
C) 0.0353 M
D) 0.0480 M
E) 0.0402 M
14) 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 0.095 M.
A) 0.085
B) 0.13
C) 0.41
D) 1.2
E) 0.95
15) 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 0.50 s?
A) 0.64
B) 1.7
C) 0.19
D) 0.11
E) 0.39
16) 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 0.11 mol/L.
A) 0.017
B) 0.68
C) 9.1
D) 40.
E) 5.2
34
17) At elevated temperatures, nitrogen dioxide decomposes to nitrogen oxide and oxygen:
NO2 (g) → NO (g) +
1
2
O2 (g)
The reaction is second order in NO2 with a rate constant of 0.543 M-1s-1 at 300 °C. If the initial [NO2]
is 0.260 M, it will take __________ s for the concentration to drop to 0.150 M.
A) 3.34
B) 0.0880
C) 1.01
D) 0.299
E) 5.19
18) 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?
A) 9.56 × 103
B) 2.85 × 104
C) 576
D) 4.33 × 1087
E) 1.36 × 102
19) 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 75.0°C if Ea = 85.6 kJ/mol?
A) 3.47 × 104
B) 1.92 × 104
C) 670
D) 3.85 × 106
E) 1.36 × 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 __________
catalyst.
11) A catalyst that is present in a different phase from the reacting molecules is called a __________
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.