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E-mail me the answer to the following questions.  If the question is a calculation, send the answer and a description of how you arrived at the answer (you need not try to type in math).  See the instructions for problem sets. (Use the "Back" button or menu command on your browser to return to this page.) 

1.  Answer Question 9 on the 1995 AP examination. (An example of an AP essay question.)  

2.  Answer Question 4 on the 1997 AP examination. (An example of an AP  free response problem.)  
  
3.  Describe how graphical methods can be used to determine the order of a reaction and its rate constant from a series of data that include the concentration of a reactant at varying times. 

4. Describe how graphical methods can be used to determine the activation energy of a reaction from a series of data that include the rate of reaction at varying temperatures. 

5. Chemical reactions occur when reactants collide. For what reasons may a collision fail to produce a chemical reaction? 

6. A study of the rate of dimerization of C4H6 (2 C4H6 -> C8H12) gave the following data:  
 

    Time, s             [C4H6], M 
   0              1.00 x 10-2  
1600              5.04 x 10-3 
3200              3.37 x 10-3 
4800              2.53 x 10-3 
6200              2.08 x 10-3
(a) Determine the average rate of dimerization (disappearance of C4H6) between 0 s and 1600 s. Between 1600 s and 3200 s. 
(b) Estimate the instantaneous rate of dimerization at 3200 s from a graph of time versus [C4H6]. What are the units of this rate? 
(c) Determine the average rate of formation of C8H12 between 0 and 1600 s and the instantaneous rate of formation at 3200 s from the rates found in parts (a) and (b).
7.  How will each of the following effect the rate of the reaction  
                    CO(g) + NO2(g) -> CO2(g) + NO(g) 
    if the rate law for the reaction is Rate = k[NO2]2? 
(a) Decreasing the pressure of NO2 from 0.50 atm to 0.250 atm. 
(b) Increasing the concentration of CO from 0.01 M to 0.03 M. 
(c) Increasing the temperature.
8.  What is the half-life for the decomposition of NOCl when the concentration of NOCl is 0.15 M? The rate constant for this second order reaction is 8.0 x 10-8 L mol-1 s-1. 

9.  An elevated level of the enzyme alkaline phosphatase (ALP) in the serum is an indication of possible liver or bone disorder. The level of serum ALP is so low that it is very difficult to measure directly. However, ALP catalyzes a number of reactions, and its relative concentration can be determined by measuring the rate of one of these reactions under controlled conditions. One such reaction is the conversion of p-nitrophenyl phosphate (PNPP) to p-nitrophenoxide ion (PNP) and phosphate ion. Control of temperature during the test is very important; the rate of the reaction increases 1.47 times if the temperature changes from 30C to 37C. What is the activation energy for the ALP-catalyzed conversion of PNPP to PNP and phosphate? 

10.  Given the rate law indicated, which of the following equations could describe elementary reactions? 
 

(a)  Cl2 + CO -> Cl2CO         Rate = k[Cl2]3/2[CO] 
(b)  PCl3 + Cl2 -> PCl5        Rate = k[PCl3][Cl2] 
(c)  2NO + H2 -> N2O + H2O     Rate = k[NO][H2] 
(d)  2NO + O2 -> 2NO2          Rate = k[NO]2[O2] 
(e)  NO + O3 -> NO2 + O2       Rate = k[NO][O3]
11.   Nitric oxide, NO, is involved in the decomposition of ozone by the mechanism 
         Sunlight 
     O3 ----------> O2 + O 
O3 + NO ----------> NO2 + O2 
NO2 + O ----------> NO + O2
 Is NO a catalyst for the decomposition? Explain your answer. 
12.  The rate of the reaction 2NO(g) + O2(g)  ->  2NO2(g) at 380oC is given by 
rate = 2.6 x 103[NO]2[O2]
The rate of the reverse reaction at 380oC is given by 
rate = 4.1[NO2]2
What is the equilibrium constant for the reaction at 380oC?
13.  One possible mechanism for the reaction of Cl2 with CO is 
       Cl2 = 2 Cl (fast)  
  Cl + CO -> COCl (slow)  
Cl + COCl -> COCl2 (fast) 
 (a) Write the rate equation for the slow elementary reaction. 

(b) Write the equilibrium constant expression for the first elementary reaction. 

(c) Solve the equilibrium constant expression from part (b) for [Cl], and substitute this concentration into the rate equation from part (a) to obtain the overall rate equation for this mechanism.

14.  For the reaction A -> B + C the following data were obtained at 30C. 
Experiment     [A], mol L-1         Rate, mol L-1 h-1 
    1             0.170                   0.0500 
    2             0.340                   0.100 
    3             0.680                   0.200

(a)  What is the rate equation, and what is the order of the reaction? 

(b)  Calculate the rate constant for the reaction. 

(c)  The equilibrium constant for the reaction is 0.500. Assume the reaction proceeds by a one-step mechanism and calculate the rate constant for the reverse reaction.

 

The following problems are examples of AP-type questions that combine two different topic areas.  
 

15.  Explain why an egg cooks more slowly in boiling water in Denver than in New York City. Hint: Consider the effect of temperature on reaction rate and the effect of pressure on boiling point. 

16.  Two reactions could initiate the pyrolysis of ethane to ethylene: 

C2H6 -> 2CH3  
C2H6 -> C2H5 + H
In these reactions, the activation energy is essentially equal to the bond energy of the bond broken in the reaction. Explain why the first of these reactions should be more effective than the second reaction in initiating the pyrolysis of ethane to ethylene.
 
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