Unit 10
Practice
Test
Kinetics
Multiple Choice Questions
Questions 1–2
2 NO(g) + H2(g) N2(g) + 2 H2O(g)
The oxidation of diatomic hydrogen by nitrogen oxide occurs at 1300 ˚C according to the reaction shown above. The
experimental rate law of the reaction is: r = k[NO]2
[H2]
1. What is the order of the reaction with respect to NO ?
(A) 1 (B) 2 (C) 3 (D) 5 E) 6
2. According to the rate law for the reaction, an increase in the concentration of diatomic hydrogen has what effect on
this reaction?
(A) The rate of reaction increases. (B) The rate of reaction decreases. (C) The rate constant increases (D) The rate constant decreases
(E) Neither the rate nor the rate constant is changed.
3. A(g) + 2 B(g) C(g)
When the concentration of substance A in the reaction above is halved, all other factors being held constant, it is found that the rate of the reaction remains unchanged. The most probable explanation for this observation is that (A) the order of the reaction with respect to substance A is 1/2
(B) substance A is not involved in any of the steps in the mechanism of the reaction
(C) substance A is not involved in the rate–determining step of the mechanism, but is involved in subsequent steps (D) substance A is probably a catalyst, and as such, its effect on the rate of the reaction does not depend on its
concentration
(E) the reactant with the largest coefficient in the balanced equation generally is rate determining
4. Step 1. Cl2(g) 2Cl(g) (fast equilibrium)
Step 2. Cl(g) + CHCl3(g) HCl(g) + CCl3(g) (slow)
Step 3. Cl(g) + CCl3(g) CCl4(g) (fast)
Chlorine gas reacts with chloroform (CHCl3) to yield hydrogen chloride and carbon tetrachloride. This
decomposition is believed to occur according to the reaction mechanism above. The rate law that is consistent with this mechanism is given by which of the following?
(A) Rate = k [Cl][CHCl3]
(B) Rate = k [Cl2][CHCl3]
(C) Rate = k [Cl2]2
[CHCl3]
(D) Rate = k [Cl2]1/2
[CHCl3]
(E) The rate mechanism is not consistent with the stated reaction
5. rate = k[X]2
For the reaction whose rate law is given above, a plot of which of the following is a straight line?
A. [X] versus time B. ln [X] versus time C. 1/[X] versus time
6. Which of the following is a graph that describes the pathway of reaction that is exothermic and has the highest acti-vation energy? A. B. Po te nt ia l E ne rg y
Reaction Coordinate Po
te nt ia l E ne rg y Reaction Coordinate
C. D. E.
Po te nt ia l E ne rg y
Reaction Coordinate Po
te nt ia l E ne rg y Reaction Coordinate
7. (CH3)3CCl(aq) + OH- (CH3)3COH(aq) +
Cl-For the reaction represented above, the experimental rate law is given as follows. Rate = k[(CH3)3CCl]
If some solid sodium hydroxide is added to a solution that is 0.010–molar in (CH3)3CCl and 0.10–molar in NaOH, which of the following is true? (Assume the temperature and volume remain constant.)
A. Both the reaction rate and k increase.
B. Both the reaction rate and k decrease.
C. Both the reaction rate and k remain the same.
D. The reaction rate increases but k remains the same.
E. The reaction rate decreases but k remains the same.
8. Relatively fast rates of chemical reaction are associated with which of the following?
A. The presence of an inhibitor
B. Low temperature
C. Low concentration of reactants
D. Strong bonds in reactant molecules
E. Low activation energy
9. The energy diagram for the reaction X + Y Z is shown above. The addition of a catalyst to this reaction would
not cause a change in which of the indicated energy differences?
A. I only B. II only
C. III only D. I and II only
E. I, II, and III
10. The reaction of nitric oxide with hydrogen occurs according to the reaction: 2 NO(g) + 2 H2(g) N2(g) + 2 H2O(g)
The rate constant for this reaction is, k = 1.1 M-2s-1. What is the overall order of the rate law?
(A) 0 (B) 1 (C) 2 (D) 3 E) 4
11. The reaction of peroxydisulfate ion (S2O82-) with iodide ion (I-) is
S2O82- (aq) + 3I- (aq) 2SO42- (aq) + I3- (aq)
The initial rate of formation of sulfate was determined to be 2.1 x 10-4 M/s. What is the initial rate of disappearance of
iodide?
(A) -2.1 x 10-4 M/s (B) -3.15 x 10-4 M/s (C) 1.1 x 10-4 M/s
(D) 2.1 x 10-4 M/s (E) 3.15 x 10-4 M/s
Time (seconds) 0 50 100 150 200
[Reactant]
(mol/L) 0.02000 0.01574 0.01298 0.01105 0.00962
12. A reaction was observed for 200 seconds and the concentration the reactant was monitored as a function of time. Which of the following best describes the order and half-life of the reaction?
Reaction Order Half-life (days)
(A) First 100
(B) First 200
(C) Second 100
(D) Second 150
(E) Second 200
14. The Arrhenius form of the rate constant is typically used in rate laws. The value of the rate constant is dependent on:
I. The concentration of reactants
II. Temperature
III. The presence of a catalyst
(A) I, II, and III (B) I and II (C) II only
(D) II and III (E) The rate constant is a constant and does not change
Part II Free Response:
Directions: Use the space provided to answer each of the following free response questions.
1. NH4+ (aq) + NO2- (aq) N2 (g) + 2 H2O (l)
The following data were obtained at 25 ˚C.
Initial Rate of Reaction,
(mol.L-1.sec-1) Initial [NH4+]o,
(mol.L-1)
Initial [NO2-]o,
(mol.L-1)
10.8 x 10-7 0.0200 0.200
10.8 x 10-7 0.200 0.0202
21.6 x 10-7 0.200 0.0404
21.5 x 10-7 0.0400 0.200
(b) Calculate the specific rate constant for this reaction and specify its units.
(c) The reaction is allowed to proceed until a volume of N2 (g) equal to 250 mL is produced. The initial reaction
concentrations in a 1.0 L container are [NH4+]o = 0.60 molar, [NO2-]o = 0.60 molar and the N2 (g) is collected over
water at 1 atm of pressure. The vapor pressure of water at 25 ˚C = 23.4 mm Hg. What is the rate of reaction at the
moment when the 250 mL container is filled.
2. CH3COOC2H5 (aq) + OH- (aq) CH3COO- (aq) + 2 C2H5 OH (aq)
The rate of the above reaction was measured at a number of temperatures and the following values of the rate constant were determined:
T = 298 K k = 0.101 M-1•s-1
T = 318 K k = 0.332 M-1•s-1
What is the activation energy associated with this reaction?
3. The following data were collected for the gas phase decomposition of nitrogen dioxide:
NO2 (g) NO(g) + O2 (g)
Time (seconds) 0 5 10 15 20
[NO2] (mol/L) 0.2000 0.034 0.018 0.0124 0.0094
a) Plot this data (on a separate sheet of paper) on the appropriate coordinate system to determine the reaction order with
respect to [NO2].
b) determine the rate constant
Time (s) [NO2] ln[NO2] 1/[NO2]
0 0.2000 -1.6 5.0
5 0.034 -3.4 29.4
10 0.018 -4.0 55.6
15 0.0124 -4.4 80.6
