Chemistry II
Worksheet 8-2
Rate Laws & Reaction Mechanisms
Name
Show your work for every calculation. Round your answer to the correct number of
significant figures and record your final answer with correct units on the line provided.
1. A reaction A + B -> C obeys the following rate law: Rate = k[A]2[B].
a. If [A] is doubled, will the rate constant change? Explain.
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b. If [A] is doubled, how will the rate change?
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c. What are the reaction orders for A and B?
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A = <*
B=
d. What is the overall reaction order?
e. What are the units of the rate constant?
2. Consider the following reaction:
2 N0(g) + 2H2(g) -» N2(g) + 2H20(g)
a. The rate law for this reaction is first order in H2 and second order in NO. Write the
rate law.
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b. If the rate constant for this reaction at 1000K is 6.0 x 104 M'V1, what is the reaction
rate when [NO] = 0.025 M and [H2] = 0.01 5 M?
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c. What is the reaction rate at 1000K when the concentration of NO is increased to 0.10
M while the concentration of H2 is 0.010 M?
3. The reaction below was studied and produced the results in the table.
2 C1O2 + 2 Off -> C1O3" + C1O2" + H2O
Experiment I"C1O71.M
TOH'I.M
Rate.M/s
0.0248
1
0.060
0.030
0.00276
2
0.020
0.030
0.00828
3
0.020
0.090
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Rate = JjJr
a. Determine the rate law for the reaction.
b. Calculate the rate constant.
c. Calculate the rate when [C1O2] = 0.010 M and [OH"] = 0.025 M.
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Chemistry II
4. The following data were collected for the rate of disappearance of NO in the following
reaction:
2ND + O2 -> 2 NO2
Experiment FNO1. M
rO?1. M
Initial Rate. M/s
1.41x10"
0.0126
0.0125
1
1.13x10'
2
0.0252
0.0250
5.64x10-2
3
0.0252
0.0125
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a. Determine the rate law for the reaction.
Rate = _Kf-
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b. What are the units for the rate constant?
c. What is the average value of the rate constant calculated from the three sets of data?
d. What is the rate of disappearance of NO when [NO] = 0.100 M and [O2] = 0.0200 M?
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5. Complete the table for each elementary reaction
Molecularity
Elementary Reaction
2 NO -> N2O2
Rate Law
Cyclopropane -> CH2=CH—CH3
S03 -^ S02 + 0
6. The decomposition of hydrogen peroxide is catalyzed by the iodide ion. The catalyzed
reaction is thought to proceed by a two-step mechanism:
H2O2(aq) + F(aq) -> H2O(1) + IO'(aq)
(slow)
lOXaq) + H202(aq) -> H2O(1) + O2(g) + F(aq) (fast)
a. Predict the rate law for the overall process.
Rate = n *~ H ^ D x A L X
b. Write the chemical equation for the overall process.
c. Identify the intermediate, if any, in the mechanism.
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7. Examine the following energy profile.
a. How many elementary reactions are in the reaction mechanism?
b. How many intermediates are formed in the reaction?
c. Which step is rate-limiting?
d. Is the overall reaction exothermic or endothermic?
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