AP Chemistry 12
Kinetics Problem Set B: Reaction Mechanisms & Activation Energy
1.
A reaction has the following mechanism:
What is the overall reaction?
2.
Write rate laws for the following elementary reactions:
a) CH3NC(g)  CH3CN(g)
b) O3(g) + NO(g)  O2(g) + NO2(g)
3.
A proposed mechanism for a reaction is
a) Write the rate law expected for this mechanism
b) What is the overall balanced equation?
c) Identify the reaction intermediates in the mechanism.
4.
Based on the following reaction profile,
a) How many intermediates are formed in the reaction A  C?
b) How many activated complexes are there?
c) Which step is the fastest?
d) Is the reaction exothermic or endothermic?
Energy
5.
The mechanism for the decomposition of NO2Cl is
NO2Cl  NO2 + Cl
NO2Cl + Cl  NO2 + Cl2
What would be the predicted rate law if the first step in the mechanism were the rate
determining step?
AP Chemistry 12
6.
Show that the following two mechanisms give the same net overall reaction.
The following questions are AP specific (i.e. not required for Chemistry 12)
7.
The following data were collected for a reaction:
Determine the activation energy for the reaction in
kJ/mol both graphically and by calculation. For the
calculation of Ea, use the first and last sets of data.
8.
Rate constants were measured at various temperatures for the reaction
HI(g) + CH3I(g)  CH4(g) + I2(g). The following data were obtained:
Determine the activation energy in kJ.mol both
graphically and by calculation. For the calculation of
Ea, use the first and last sets of data.
Answers:
1.
2NO + 2H2  N2 + 2H2O
2.
a) rate = k[CH3NC]
3.
a) rate = k[C4H9Br]
b) C4H9Br + 2H2O  C4H9OH + Br- + H3O+
c) C4H9+ and C4H9OH+
4.
a) 1
5.
rate = k[NO2Cl]
6.
It works!
7.
79 kJ/mol
8.
139 kJ/mol
b) 2
b) rate = k[O3][NO]
c) peak between A and B
d) exothermic