14) The reaction below is first order in H2 and second order in NO. What is the rate law for this reaction?
2 H2(g) + 2 NO(g) → N2(g) + 2 H2O(g)
A) Rate = 2k[H2][NO]
B) Rate = k[H2][NO]2
C) Rate = k[H2]1/2[NO]
D) Rate = 2k[H2]1/2[NO]1/2
15) The reaction shown below has the rate law: Rate = k[BrO3–][Br–][H+]2.
BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l)
What is the order of reaction with respect to Br –?
A) first
B) second
C) fifth
D) sixth
16) The reaction between chlorine and nitric oxide to form nitrosyl chloride is shown below. If the
reaction rate doubles when the concentration of Cl2 is doubled and the rate quadruples when the
concentration of NO is doubled, by what factor will the rate increase if both concentrations, NO and Cl2,
are doubled?
Cl2(g) + 2 NO(g) → 2 NOCl(g)
A) 2
B) 4
C) 8
D) 6
17) Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) → products. If the rate law is:
Rate = k[E] [F]-1, what is the order of reaction with respect to E?
A) one-half
B) second
C) first
D) one-fifth
18) Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) → products. If the rate law is:
Rate = k[E]2[F]-1, what is the overall order of reaction?
A) zero
B) one
C) two
D) one-fourth
19) Cerium(IV) ion reacts with thallium(I) ion in a one-step reaction shown below.
2 Ce4+(aq) + Tl+(aq) → 2 Ce3+(aq) + Tl3+(aq)
If the rate law is: Rate = k[Ce4+]4[Tl+]2, what is the overall order of the reaction?
A) first
B) second
C) sixth
D) eighth
61
20) If the units for rate are M s-1, what are the units for the rate constant, k, if the overall order of the
reaction is five?
A) s
B) M2 s
C) M-1 s-1
D) M–4 s-1
21) If the units for rate are M s-1, what are the units for the rate constant, k, for a zeroth-order reaction?
A) s-1
B) M
C) M s-1
D) M-1 s–1
22) For the zeroth-order reaction: C → products, –Δ[C]/Δt = k, which of the following graphs would be
expected to give a straight line?
A) [C] vs. t
B) 1/ln[C] vs. t2
C) 1/[C] vs. t
D) [C]2 vs. t2
23) For the zeroth-order reaction: A → products, what will happen to the rate of reaction if the
concentration of A is tripled?
A) The rate will be higher.
B) The rate will be tripled.
C) The rate will be one-third.
D) The rate will remain the same.
24) For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to
62
decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction?
A) 1.0 × 10-4 s-1
B) 4.8 × 10-4 s-1
C) 6.0 × 10–3 s-1
D) 2.9 × 10-2 s-1
25) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a rate constant equal to 2.20 × 10-5 s–1 at 593 K.
What percentage of the initial amount SO2Cl2 will remain after 3.00 hours?
A) 1.00%
B) 21.1%
C) 23.5%
D) 78.9%
26) The first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), has a rate constant equal to 0.76 s–1 at 1000 K.
How long will it take for the concentration of N2O to decrease to 6.0% of its initial concentration?
A) 0.27 s
B) 3.7 s
C) 13 s
D) 17 s
27) The isomerization reaction, CH3NC → CH3CN, is first order and the rate constant is equal to 0.46 s-1
at 600 K. What is the concentration of CH3NC after 0.20 minutes if the initial concentration is 0.40 M?
A) 1.6 × 10-3 M
B) 3.6 × 10-3 M
C) 1.6 × 10–1 M
D) 3.6 × 10-1 M
28) The following reaction is first order, C2H6 → 2 CH3. If the rate constant is equal to 5.5 × 10-4 s-1 at
1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.25 mol in the same
container?
A) 3.0 min
B) 10. min
C) 42 min
D) 48 min
29) The rate constant, k, for a first-order reaction is equal to 6.2 × 10-4 s-1. What is the half-life for the
reaction?
A) 4.3 × 10-4 s
B) 8.0 × 102 s
C) 1.1 × 103 s
D) 1.6 × 103 s
30) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a half-life of 8.75 hours at 593 K. How long will it
take for the concentration of SO2Cl2 to fall to 14.5% of its initial value?
A) 0.153 hr
B) 1.98 hr
C) 6.54 hr
D) 24.4 hr
31) For the first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), what is the concentration of N2O after 3 half–
lives if mol of N2O is initially placed into a 1.00-L reaction vessel?
A) 1.2 × 10-3 M
B) 2.5 × 10-2 M
C) 5.0 × 10–2 M
D) 1.0 × 10-1 M
32) In aqueous solution, hypobromite ion, BrO–, reacts to produce bromate ion, BrO3–, and bromide ion,
Br–, according to the following chemical equation.
3 BrO–(aq) → BrO3–(aq) + 2 Br–(aq)
A plot of 1/[BrO–] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of
BrO– is 1.0 M, how long will it take one-half of the BrO– ion to react?
A) 5.6 × 10-2 s
B) 8.9 s
C) 12 s
D) 18 s
33) The second-order reaction 2 Mn(CO)5 → Mn2(CO)10, has a rate constant equal to 3.0 × 109 M-1 s-1 at
25°C. If the initial concentration of Mn(CO)5 is 5.0 × 10-5 M, how long will it take for 90.% of the reactant
to disappear?
A) 1.7 × 10–15 s
B) 1.9 × 10–14 s
C) 6.0 × 10–5 s
D) 1.5 × 102 s
34) Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and
oxygen according to the following chemical equation.
2 NO2(g) → 2 NO(g) + O2(g).
A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300°C. If the half-life and the rate
constant at 300°C are 44 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the
original sample?
A) 0.042 mol
B) 0.11 mol
C) 24 mol
D) 59 mol
66
35) Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine
according to the following chemical equation.
2HI(g) → H2(g) + I2(g)
At 800 K it takes 233 seconds for the initial concentration of HI to decrease from 5.75 × 10-2 M to 2.50 × 10–
2 M. What is the rate constant for the reaction at this temperature?
A) 1.90 × 10-4 M-1s-1
B) 9.70 × 10-2 M-1s-1
C) 10.3 M-1s-1
D) 5.27 × 103 M-1s-1
36) What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68
kJ/mol at 25°C?
A) 1.2 × 10–12
B) 2.7 × 10-2
C) 27
D) 8.3 × 1011
37) The reaction A + B C + D occurs in one step. The activation energy is 132 kJ/mol and ΔE = -236 kJ/mol.
What is the activation energy for the reverse reaction?
A) -104
B) 368
C) -368
D) 104
38) The aquation of tris(1,10-phenanthroline)iron(II) in acid solution takes place according to the
equation:
Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+
If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the rate
constant at 40°C?
A) 2.0 × 10-3 min-1
B) 4.8 × 10-2 min-1
C) 2.1 × 101 min-1
D) 5.0 × 102 min-1
39) The elementary reaction: 2 HF → H2 + F2, is an example of a ________ reaction.
A) unimolecular
B) bimolecular
C) termolecular
D) tetramolecular
40) A three-step mechanism has been suggested for the formation of COCl2:
Step 1: Cl2 → 2 Cl
Step 2: Cl + CO → COCl
Step 3: COCl + Cl2 → COCl2 + Cl
Which species is an intermediate in the mechanism?
A) Cl
B) CO
C) COCl
D) COCl2
41) The slowest step in a reaction mechanism is called the ________ step.
A) termination
B) elementary
C) rate law
D) rate-determining
42) Which general rate law below corresponds to an elementary bimolecular reaction?
A) Rate = k[B]
B) Rate = k[A][B][C][D]
C) Rate = k[A] [B]2
D) Rate = k[A]2
43) What is the rate law for the elementary reaction shown below?
2 HI → H2 + I2
A) Rate = k[HI]
B) Rate = k[HI]2
C) Rate = k[H2][I2]
D) Rate = k[H2][I2]/[HI]2
44) A gaseous reaction occurs by a two-step mechanism, shown below.
Step 1: AX +Y2 ⇌ AXY2 fast
Step 2: AXY2 + AX → 2 AXY slow
Including concentration of only reactants and products, what is the rate law for this reaction?
A) Rate = k[AX][XY2]
B) Rate = k[AXY2]/[AX][Y2]
C) Rate = k[AX]2[Y2]
D) Rate = k[AXY]2/[A Y2][AX]
45) A catalyst increases the rate of a reaction by providing a different reaction pathway that
A) lowers only the activation energy.
B) raises only the energy of the products.
C) lowers only the energy of the reactants and products.
D) All of these are affected by the presence of a catalyst.
46) The decomposition of hydrogen peroxide is given by the following reaction:
2 H2O2(aq) → 2 H2O(l) + O2(g)
In the presence of KI the reaction is thought to occur by the following mechanism:
Step 1: H2O2 + I– → H2O + IO–
Step 2: IO– + H2O2 → H2O + O2 + I–
What is the role of I– in this mechanism?
A) catalyst
B) frequency factor
C) product
D) transition state
47) An aqueous reaction occurs by a two-step mechanism, shown below.
Step 1: A2X2 + Y → A2X + XY
Step 2: A2X2 + XY → A2X + X2 + Y
What is the catalyst in this reaction?
A) A2X2
B) X2
C) XY
D) Y
48) A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3(g) + HO(g) → HO2(g) + O2(g)
Step 2: HO2(g) + O(g) → HO(g) + O2(g)
Which species is a catalyst and what type of catalysis is occurring?
A) HO, homogeneous
B) HO, heterogeneous
C) O3, homogeneous
D) O , heterogeneous
49) The Haber process is the synthesis of ammonia gas from hydrogen and nitrogen on a hot metal
surface. What is the catalyst and what type of catalysis is occurring?
A) H2, heterogeneous
B) N2, heterogeneous
C) NH3, heterogeneous
D) metal surface, heterogeneous
50) Biological reactions are catalyzed by
A) sugar.
B) enzymes.
C) fats.
D) water.
13.3 Short Answer Questions
1) For the reaction shown below, if the rate of formation of O2 is 6.5 × 10–6 M/s, the rate of decomposition
of N2O5 over the same time interval is ________.
2 N2O5(g) → 4 NO2(g) + O2(g)
2) For the reaction shown below, the rate of reaction of Br – is ________ times the rate of formation of Br2
over the same time period.
ClO2–(aq) + 4 Br–(aq) + 4 H+(aq)→ Cl–(aq) + 2 Br2(aq) +2 H2O(l)
3) For the reaction shown below, if the rate of formation of Br2 is 1.5 × 10-6 M/s, over the same time
period the rate of consumption of H+ is ________ M/s.
ClO2–(aq) + 4 Br–(aq) + 4 H+(aq)→ Cl–(aq) + 2 Br2(aq) +2 H2O(l)
4) The reaction below is first order in H2 and one-half order in Br2. The rate law for this reaction is
________.
H2(g) + Br2(g) → 2 HBr(g)
5) The reaction shown below has the rate law: Rate = k[BrO3–][Br–][H+]2. The order of reaction with
respect to H+ is ________ and the overall order is ________.
BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l)
6) A reaction has the rate law Rate = k[NO]2[H2]. If the concentration of NO is reduced by 1/3, the rate of
reaction will be ________ (increased, decreased) by ________.
7) A reaction has the rate law Rate = k[NO]2[H2]. If the concentration of NO is reduced by half and the
concentration of H2 is quadrupled, the rate of reaction will ________ (increase, decrease, not change).
8) The reaction below is second order in ClO2 and first order in OH–. If the rate is expressed in M/s, the
rate constant, k, has the units ________.
2 ClO2(aq) + 2 OH–(aq) → ClO3–(aq) + ClO2–(aq) + H2O(l)
9) The reaction below is second order in ClO2 and first order in OH–. When the concentration of ClO2 is
0.020 M and the concentration of OH– is 0.10 M, the initial rate of reaction is 8.00 × 10-4 M/s. What is the
rate constant, k, for this reaction?
2 ClO2(aq) + 2 OH–(aq) → ClO3–(aq) + ClO2–(aq) + H2O(l)
10) A reaction is second order in NO and first order in O2 has a rate constant, k = 1.4 × 104 M-2s-1. What is
the initial rate of reaction when the concentrations of NO and O2 are 0.015 M and 0.030 M, respectively?
11) At 300°C decomposition of NO2(g) occurs with a rate law: Rate = – k[NO2]x. If the initial rate of
decomposition is 3.2 × 10–5 M/s when [NO2]o = 8.0 × 10-3 M and the initial rate of decomposition is 8.0 ×
10–6 M/s when [NO2]o = 4.0 × 10-3 M, then the order of reaction with respect to NO2, x = ________.
12) A gaseous compound, C, undergoes catalytic decomposition at an initial rate of 0.45 M/s when [C]o =
3.0 × 10-3 M and 0.45 M/s when [C]o = 9.0 × 10-3 M. Therefore, this is a ________ order reaction.
13) The decomposition of hydrogen peroxide occurs according to the equation
2 H2O2(aq) → 2 H2O(l) + O2(g)
A concentration-time study of this reaction produces a straight line when ln[H2O2] is plotted versus time.
Therefore, this is a ________ order reaction.
14) At 55° the decomposition of N2O5 is first order, having a rate constant, k = 1.7 × 10-3 s-1. If the initial
concentration of N2O5 is 6.4 × 10–3 M, the number of half-lives that are required for the N2O5
concentration to fall to 2.0 × 10-4 M is ________, and the amount of time required is ________ minutes.
15) At an elevated temperature the decomposition of a gaseous oxide, AO2 occurs with a rate constant,
k = 0.54 M-1s-1. If the half-life of this reaction is 926 seconds when [AO2] = 2.0 × 10-3 M and 462 seconds
when [AO2] = 4.0 × 10-3 M, this reaction is ________ order.
16) A reaction has a rate constant, k = 1.2 × 10–12 s-1 at 273 K and k = 5.1 × 10-7 s-1 at 373 K has an
activation energy, Ea = ________ kJ/mol.
17) A reaction with an activation energy, Ea = 51.2 kJ/mol will proceed ________ times faster when the
temperature is raised from 20 °C to 30 °C.
18) A reaction with an activation energy, Ea = 103 kJ/mol has a rate constant, k = 3.5 × 10-5 s-1 at 25°C. For
this reaction the rate constant at 45°C is ________.
19) The rate-determining step in a reaction is shown below. The molecularity of this reaction is ________.
NO2(g) + NO2(g) → NO(g) + NO3(g)
20) A reaction occurs by a two-step mechanism, shown below.
Step 1: AX2(g) → AX(g) + X(g)
Step 2: AX2(g) + X(g) → AX + X2(g)
The intermediate in this reaction is ________, and the molecularity of the second step is ________.
21) A gaseous reaction occurs by a two-step mechanism, shown below.
Step 1: CX + W2 → CXW2
Step 2: CXW2 + CX → 2 CXW
If the rate law for this reaction is Rate = k[CX]2[W2], the intermediate is ________, and step ________ is
the rate-determining step.
22) An aqueous reaction occurs by a two-step mechanism, shown below.
Step 1: A2X2 + Y → A2X + XY
Step 2: A2X2 + XY → A2X + X2 + Y
In this reaction the intermediate is ________, and the catalyst is ________.
23) Hydrochloric acid in the hydrolysis of an ester to form an alcohol and a carboxylic acid is an example
of a ________ (heterogeneous, homogeneous) catalyst.
24) Platinum in the catalytic converter of an automobile catalyzes the conversion of CO to CO2 is an
example of a ________ (heterogeneous, homogeneous) catalyst.