Kinetics Test
PSI AP Chemistry Name________________________________
Section 1 Multiple choice
1) A + B C + D
The rate law for the hypothetical reaction shown above is R = k[A].
Which of the following changes to the system will increase the rate of the reaction?
I an increase in the concentration of A II an increase in the concentration of B III an increase in the temperature
A) I only B) I and II only C) II and III only D) I and III only E) I II and III
2) Given the data below for the reaction yY + zZ products
Trial [Y] (M) [Z] (M) Initial rate (M/s)
1 0.100 0.100 4.0 x 10-5
2 0.200 0.100 1.6 x 10-4
3 0.100 0.200 8.0 x 10-5
The rate law is
A) k[Y][Z] B) k[Y]2[Z] C) k[Y]2[Z]2 D) k[Y][Z]2 E) k[Y]4[Z]2
3) Which of the following best describes the role of the spark from the spark plug in an
automobile engine?
(A) The spark decreases the energy of activation for the slow step. (B) The spark increases the concentration of the volatile reactant.
4) Which of the following has a rate constant with units of L2 mol-2 s-1
A) R= k[A] B) R= k[A]2 C) R= k[A][B] D) R= k[A][B]2 E) R= k[A]0
5) The specific rate constant of a natural isotope is 3.32 x10-15 . The half life of this
isotope is ---years. A) 3 x1014
B) 2 x 1014 C) 2 x10-14 D) 2 x1013 E) 3 x1013
6) The reaction mechanism for the chlorination of trichloromethane is shown below:
Cl2 (g) 2 Cl (g) (fast)
Cl (g) + CHCl3 (g) HCl (g) + CCl3 (g) (slow)
Cl (g) + CCl3 (g) CCl4 (g) (fast)
Which of the following is an intermediate in the reaction? I. Cl
II. Cl2 III. CCl3 IV. CHCl3
7) Hydrogen peroxide decomposes according to the reaction
2 H2O2 (l) 2 H2O (l) + O2 (g)
which is first order for H2O2 and has a half-life of 18.0 minutes. If an H2O2 solution that was initially 0.80 M is allowed to decompose for 72 minutes, what will be the
concentration be at that time? (Assume volume change is negligible.)
A) 0.05 M B) 0.10 M C) 0.20 M D) 0.40 M E) 0.80 M
8) H2 (g) + I2 (g) 2 HI (g)
When the reaction above takes place in a sealed isothermal container, the rate law is Rate=k[H2][I2]. If one mole of hydrogen gas is added to the reaction chamber, which of the following will be true?
A) The rate of reaction will increase and the rate constant will not change. B) The rate of reaction will not change and the rate constant will increase. C) The rate of reaction and the rate constant will increase.
D) The rate of reaction and the rate constant will not change
E) The rate of reaction will increase and the rate constant will decrease.
9) 2 ClO2+ 2F2 ClO2F
The mechanism for the overall reaction above is:
Step 1 ClO2 + F2 ClO2F2 (slow)
Step 2 ClO2F2 + F2 F (fast)
Step 3 ClO2 + F ClO2F (fast)
The rate law for the reaction is:
10) Which substance in the reaction below disappears the slowest?
4NH3 +7O2 4NO2 + 6H2O
A) NH3 B) O2 C) NO2 D) H2O
E) The rates of appearance/disappearance are the same for all of these.
11) 2 C6H6 (g) + 15 O2 (g ) 12 CO2 (g) + 6 H2O (l)
The rate at which CO2 is produced in the reaction above is 6.0 M/s. What is the rate at which O2 is consumed?
A) 4.0 M/s B) 6.0 M/s C) 7.5 M/s D) 15 M/s E) 30 M/s
12) For a first-order reaction, a plot of __________ versus __________ is linear.
A) ln A
t, t B) ln [A]t, 1
t C)
1
[A]t, t D) A t, t E) t,
1 [A]t
13) Which one of the following graphs shows the correct relationship between
concentration and time for a reaction that is second order in [A]?
A)
B)
C)
D)
E)
14) The rate of the chemical reaction between substances A and B is found to follow the rate law Rate = k[A]2[B] where k is the rate constant. The
concentration of A is reduced to half its original value. To make the reaction proceed at 50% of its original rate the concentration of B should be:
A) Decreased by ¼ B) Halved
C) Kept constant D) Doubled
E) Increased by a factor of 4
15) Given the mechanism below for the oxidation of nitrogen dioxide, determine the rate law expression for the overall reaction.
K1
Step 1 (fast) NO + NO N2O2 K2
K3
Step 2 (slow) N2O2 + O2 2 NO2
A) k3 [N2O2][O2]
B) (k1k3)/k2 * [NO]2[O2]
C) (k2k3)/k1 * [NO]2[O2]
Section II Free Response
1)
A (aq) + 2 B(aq) 3 C(aq) + D(aq)
For the reaction above, carried out in solution of 25C, the following kinetic data were obtained:
Experimen t
Initial Conc. of Reactants (mole.liter-1)
Initial Rate of Reaction (mole.liter-1.hr-1)
Ao Bo
1 0.240 0.120 2.00 2 0.360 0.240 9.00 3 0.120 0.120 0.500 4 0.014 0.135 ?
a) Write the rate-law expression for this reaction. Justify your answer.
b) Calculate the value of the specific rate constant k at 25C and specify its units.
c) Calculate the value of the initial rate of this reaction at 25C in experiment 4. d) Assume the reaction 2 is reached to completion. What would be the amount of C
produced at the end of the reaction?
e) During the analysis for a first order decomposition of 1.0M H2O2 , the plot below was produced.
Time (min)
i) Label the vertical axis of the graph
ii) On the graph, draw the line that represents the catalyzed first order
decomposition of 1.0M H2O2 (aq) (correct starting point and slope of the line will earn full credit).
f) An environmental concern is the decomposition of ozone, O3, in earth’s atmosphere, where ozone is normally in equilibrium with O2 and O. A proposed mechanism for the decomposition of O3 in the upper atmosphere is shown below.
Step1 O3 + Cl O2 + ClO Step2 ClO + O Cl + O2
Answer:
1. D 2. B 3. C 4. D 5. B 6. D 7. A 8. A 9. A 10. A 11. C 12. A 13. C 14. D 15. B
Free response:
a) Expt. 1 and 3 : B kept the same and A doubled. The rate increased by 4 times. With respect to A it is second order.
Expt. 2 and 3: 2 0.362 x 0.24x
___ = --- = 9/0.500 3 0.122 x 0.12x
X= 1, with respect to B the order is one. R = k[A]2[B]
b) k = R/ [A]2[B] k = (2)/(0.240)2(0.120) = 289.35mol-2L2hr-1 c) R4 =289.35x(0.014)2(0.135) = 0.00766
d) B is the limiting.
2B/3C = 0.24/X C = X = 0.36 e) i) ln[H2O2]
ii) The new line should start at the same starting point. It should be below the original line with a steep slope.